The Charity Commission has launched a statutory inquiry into Oxfam amid concerns that the scandal-hit charity may not have 'fully and frankly disclosed' all details about allegations of sexual assault and the use of prostitutes in Haiti in 2011.

The news came as Oxfam's leadership issued an 'unreserved apology' to the government, donors, supporters and the people of Haiti.

The charity's deputy chief executive, Penny Lawrence, has resigned, saying that she took full responsibility for what had happened on her watch and was sorry for the 'harm and distress' it had caused supporters.

But the charities watchdog said that Oxfam may not have 'fully and frankly disclosed material details about the allegations at the time in 2011' and that it also had concerns about Oxfam's handling of the incidents subsequently.

The commission's deputy chief executive David Holdsworth said: 'Charities and dedicated, hard-working aid workers undertake vital, lifesaving work in some of the most difficult circumstances across the world.

'However, the issues revealed in recent days are shocking and unacceptable. It is important that we take this urgent step to ensure that these matters can be dealt with fully and robustly.'

Oxfam received £31.7m in Government funding in 2016/17, but ongoing support has been put at risk by the scandal.

The Charity Commission's chief executive, Helen Stephenson, met yesterday with the Secretary of State for International Development, Penny Mordaunt. 'They both agreed that charities need to do more to ensure high standards of safeguarding and set the right culture and tone at the top and are committed to ensuring that this is the case. We are pleased to announce, with DFID, that we will be calling in key international aid charities to a summit on safeguarding as soon as possible in the coming weeks, paving the way for a significant conference,' the commission said.

'It is vital that trustees set a culture within their charity that prioritises safeguarding so that it is safe for those affected to come forward and report incidents and concerns with the assurance they will be handled sensitively and properly by charities. Full and frank disclosure to the regulator and the relevant authorities, nationally and internationally, is also key. Everybody has the right to be safe, and the public rightly expects charities to be safe and trusted places for all who they come into contact with.'