Around £27,000 of the total went on air travel, including business class flights across the Atlantic.

A further £6,700 was spent on rooms in a "landmark" Washington hotel for the March 12-18 stay.

The size of the delegation, which included MLAs from Northern Ireland's four main parties, was today questioned by Alliance leader David Ford.

The Policing Board, however, has issued a positive assessment of the visit and concluded that its "key aims" were achieved.

The delegation included chairman Sir Desmond Rea, vice chairman Barry Gilligan, Alex Maskey of Sinn Fein, the UUP's Basil McCrea, ex-DUP Minister Ian Paisley Jnr and Dolores Kelly of the SDLP. Two Board officials accompanied the members.

The purpose of the visit included representing the Policing Board at this year's St Patrick's Day reception in the White House. A series of meetings was also held with US politicians, policing bodies and other organisations.

Details of the expenditure have been disclosed under freedom of information.

The Board said flight costs totalled £27,087.30, involving business class flights from Dublin to Washington, coach class from Washington to Newark and business class from Newark to Belfast.

Travel costs to and from the airport totalled £569.29 and travel insurance £600.

The grouping stayed at the Georgetown Inn in Washington, at a cost of £6,790.50.

It describes itself on its website as a "luxury", "landmark" hotel, boasting "traditional allure and close proximity to the picturesque Georgetown waterfront".

Taxi costs while in Washington came to £120.50, the freedom of information disclosure stated.

The overall cost of the visit was given as £35,167.59.

Mr Ford today commented: "It appears that anything involving the Executive or Policing Board requires all four of the parties to be represented, such is their limited trust in each other.

"Given the moves towards normality, I'm not convinced of the need for such a representation of the Board in this case. It could be adequately represented by the chair and vice chair."

The Alliance leader also said: "Travelling by business class for a stay of this length adds to the questions raised."

The Washington trip expenditure is roughly equivalent to the cost of putting 1.5 new PSNI constables on the beat for 12 months.

A Policing Board assessment of the trip said: "The key aims and objectives set for the visit were realised through the programme of events/meetings completed.

"Board members were well received, with significant recognition for the progress made on policing, including the delivery of full political support for policing; and the achievements of the Northern Ireland Policing Board and the Police Service of Northern Ireland."

It also stated: "The meetings, both formal and informal, provided a platform to promote and inform the work of the Board, and key challenges ahead for policing."

The programme for the visit included discussions with Congressmen from the Friends of Ireland Group and a meeting with a representative of Senator Ted Kennedy's office.

There were also visits to two police departments in the States and a meeting with the US Police Executive Research Forum.

As well as the traditional White House Shamrock St Patrick's Day ceremony, Board delegation members attended an Irish Ambassador's reception and a dinner hosted by the British Ambassador.

The official aims of the visit included outlining the work and achievements of the Policing Board, setting out the challenges for policing "in advance of devolution of policing and justice", and increasing the profile of the Board "among key influencers and opinion formers".