Channel 4's CEO has said she is "deeply sorry" over the rape allegations from cast members on Married at First Sight UK, adding that the women's distress was "clear".

An investigation by BBC Panorama heard from two women who said they were raped by their on-screen husbands, and a third who alleged a non-consensual sex act.

Channel 4 boss Priya Dogra previously declined to apologise when asked by a reporter following the broadcast of Panorama on Monday, although she did express her "sympathy" for those who had spoken up.

But speaking at a press briefing on Wednesday to mark the release of the network's annual report, she apologised and said she had found the women's accounts "very troubling" to watch.

Dogra also clarified that the latest season of MAFS UK – which has already been filmed – has not been axed, despite media reports to the contrary.

In a separate development on Wednesday, holiday company Tui said it had decided to end its sponsorship of MAFS UK following the Panorama broadcast and discusssion with Channel 4.

Earlier this week, Tui had told BBC News they were "pausing" their sponsorship activity.

Addressing journalists at the briefing on Wednesday, Dogra said she wanted to start by addressing the Panorama programme.

"I have watched the programme, and heard the women's accounts, which are very troubling," she said. "Their distress is clear, and for that, I am of course deeply sorry."

She added that welfare across all Channel 4 programmes is "hugely important" and "a primary concern".

But she said Channel 4 can't investigate the women's allegations, which the men have denied, adding: "We are a broadcaster, not an adjudicator."

Last month, Channel 4 commissioned an external review into welfare on the show.

Dogra said the review was commissioned "just days" after first being contacted by the BBC in April.

That review is under way, she said, and is expected to be completed later this summer.

"I do believe that our handling of concerns at the time was appropriate but as I only took this role up recently, I wanted this looked at again," she said.

On Monday, all episodes of MAFS UK were pulled from the broadcaster's streaming and linear services and its social channels.

Dogra explained this decision was made prior to the Panorama broadcast, as she "didn't want to run the risk of stoking speculation that might lead to jigsaw identification of the women" in the film.

Turning to media reports that the show has been cancelled, Dogra called these "wholly inaccurate".

"No decision has been made on the broadcast of MAFS UK series six. Any decision we do take, will be made only after the review has concluded," she said.

During the briefing, Dogra took questions from journalists which were dominated by the issue of MAFS UK.

When asked by BBC News why Channel 4 has now commissioned two investigations, when it said as recently as last week that the allegations are, in its view, "wholly uncorroborated", Dogra responded: "Our job is to look at our actions, our job is to look at our protocols and how we applied them.

"It is for other people to look into allegations that the women have made, our job is to look at allegations of a duty of care failure. That's the distinction between the two."

Ian Katz, the outgoing chief content officer, added that he was "very confident" that based on the knowledge Channel 4 had at the time, it had made "the right decisions".

BBC News also asked Channel 4 whether, as a public service broadcaster, it would have been more transparent to make the review public when it was launched last month – and whether it waited until it was clear the Panorama broadcast was going ahead before announcing it.

Dogra responded by saying Channel 4 was always going to publish the outcome of the review, adding: "I don't know that we needed to say anything about it in advance. I don't think we were waiting for the Panorama to conduct the work."

Meanwhile, a group of MPs has written to Channel 4 to ask for answers about what they say are "horrifying" allegations aired by Panorama.

The House of Commons Culture, Media and Sport Committee has written to both Channel 4 and broadcast regulator Ofcom with questions about their actions and responses to the claims.

"The horrifying allegations about Married at First Sight raise serious concerns over whether enough is being done to protect people taking part in reality television," the committee's chairwoman Caroline Dinenage MP said.

"Both Channel 4 and Ofcom, as the broadcasting regulator, have urgent questions to answer."

The letter to Channel 4 asks the network about the complaints process for contestants on the programme, the steps taken to ensure the allegations were fully investigated, and the review announced by the broadcaster.

It also asks about Channel 4's approach to duty of care to participants on its other reality TV programmes.

A separate letter from the committee to Ofcom asks about the regulator's role in the complaints process, its powers to investigate potential breaches of the broadcasting code, and the timeline for launching its own investigation into the Married at First Sight allegations.

Lawyers for CPL, the independent production company that makes the UK version of the show, said its welfare system was "gold standard" and industry-leading, and that it acted appropriately in all these cases.

Married at First Sight UK - known to many as MAFS - sees single people agree to "marry" total strangers, after meeting for the first time at their mock weddings.

The marriages are not legally binding, but viewers see the couples go on "honeymoon", before moving in together and navigating their relationships - all while being filmed, almost every day.

On Tuesday, police urged potential victims of sexual assault on reality TV show Married At First Sight UK to get in touch.

A Metropolitan Police spokesperson said: "At this time, we have not received any criminal reports in relation to this matter.

"We will be making approaches to the relevant production teams to ensure that anyone they have spoken to is aware of how to report any criminal allegations to police.

"We continue to encourage anyone who believes they have been a victim of sexual assault, no matter how long ago it happened, to get in touch with us."

Additional reporting by Steven McIntosh.