The Cumbria-based head of trustees at Oxfam has urged the charity to be open and honest about workers involved in sex scandals.

The allegations include one woman who was coerced into sex to receive aid, and sex parties held by aid workers sent to Haiti in the wake of the 2011 earthquake which killed 220,000.

Caroline Thomson, the chairwoman of the charity's trustees, says she will help tighten up recruitment and ensure the charity is more open and transparent.

Ms Thomson has cancelled a holiday in Madeira with husband Lord Roger Liddle, a Cumbria county councillor, to deal with the situation.

She is understood to have met Penny Mordaunt, the Secretary of State for International Development to discuss the scandal.

The former chief operating officer of the BBC, who became chairman of the trustees in October, said she felt "anger and shame" over the behaviour highlighted in Haiti in 2011.

In a statement she said: "It is clear such behaviour is completely outside our values and should never be tolerated.

"In the words of our chief executive Mark Goldring, we are ashamed of what happened. We apologise unreservedly."

The Charity Commission is to investigated Oxfam's handling of a sex scandal where prostitutes were hired in Haiti in 2011.

Oxfam's deputy chief executive Penny Lawrence has resigned and Ms Thomson, who lives near Wigton, said: "We will continue to address the underlying cultural issues that allowed this behaviour to happen.

"Earlier this year, our board of trustees appointed an independent consultant to review how we can better promote and enforce a positive culture right through all of our workforce and drive out unacceptable behaviour."

She pointed out the review was part of a package of measures to strengthen the vetting of staff and improving positive behaviour.

Ms Thomson added: "As recent events have shown, sexual abuse is a blight on society and Oxfam is not immune.

"We have made significant improvements since 2011 in our efforts to expose and eliminate sexual abuse but we know we have to be vigilant and to continue to improve."

Tony Vaux worked for Oxfam from 1972 to 2000 including six years living in India and about 20 years managing emergency responses.

He covered famine in Ethiopia and wars in Mozambique, Sudan, Somalia and Afghanistan. He was also regional manager for eastern Europe and the former Soviet Union.

After Oxfam, he was a consultant on conflict and fragile states including policy analysis, research studies and evaluation, regularly working with the government.

He is shocked by the recent revelations and says the storm that has hit the charity is similar to the sex scandals that have hit Hollywood and also Westminster in recent months.

He says aid workers have abused their positions of power and used it to take advantage of women in vulnerable situations.

He fears that Oxfam and likely other charities, have been infiltrated by predators who see it as an easy world in which to operate and prey on people.

Mr Vaux, who lives near Wigton, says charities should be more accountable to rules and regulations imposed by authorities where the aid workers are based, rather than operating under their own rules.

"The aid sector has been caught up rather belatedly in the kind of thing that can happen and will happen because of the abuse of power.

"It is the same thing that has happened in film making and even in the Houses of Parliament where there is that kind of power and a sort of immunity, you will get abuse and people taking advantage of it in ways that are quite astonishing.

"People say 'who would do that sort of thing?' When I was in Oxfam we simply did not think that way, we thjought everyone coming into aid was doing it for a good reason. Or perhaps we just did not know it was happening."

He fears the reports on Oxfam workers could be just the tip of the iceberg concerning charity workers involved in abuse cases.

He says that while Oxfam and Save The Children have both launched enquiries into allegations and complaints against aid workers, other organisations have not.

"Oxfam and Save The Children are the only agencies that have come up with any serious information about this. Other big organisations have not been able to.

"That means they don't actually know about it, or have mnade serious efforts to find out.

"I'm sure it is not a problem restricted to Oxfam."