Details of a controversial trip to London on the government jet by minister Noel Dempsey have been censored by the Department of Transport on the basis that it would not be in the public interest to know what he was doing in the English capital.

The Gulfstream IV was used to fly Dempsey first to a summer school in Donegal and then onwards to England for a secretive meeting the following day. The cost of the trip was €23,000.

Details of the minister's London engagement in July were sought under the Freedom of Information Act by the Sunday Tribune. However, precise records regarding whom Dempsey met and what they spoke about has been censored from the released documents.

The Department of Transport did not provide a precise explanation for redacting the documents but said access had been refused on various grounds.

It said allowing the Irish people to know exactly what the minister was doing in London would "be contrary to the public interest".

Three sections of the Freedom of Information Act were specified in the department's refusal, all of which seem to suggest the meeting related to a government contract.

An itinerary for the trip simply says Dempsey was collected from his hotel and taken to the Irish embassy. At 8am, he sat down for a 90-minute breakfast discussion, which was described as "critical" by department civil servants.

The previous day, Dempsey and his private secretary, Veronica Scanlon, had gone on a 40-minute flight from Dublin to Derry. Dempsey had been asked to make a contribution to the MacGill summer school, which was taking place in Glenties, Co Donegal, at the time.

At eight o'clock that evening, the minister and his private secretary headed back to Derry airport from where they flew for 70 minutes to London Gatwick.

The following morning, they returned to Gatwick and were picked up by the Gulfstream IV, which took them back to Dublin.

The final cost of the round-trip is estimated at €23,000, with additional expenses incurred because of a decision to send the minister's state car to Derry to meet him.

In the immediate aftermath of controversy over the arrangements, Dempsey said that, with the "wonderful benefit of hindsight", an alternative should have been considered.

The London meeting had been organised well in advance and letters were sent from Dempsey to the Department of Foreign Affairs, the Department of the Taoiseach and the Department of Justice to inform them.

Another letter sent to the department of the taoiseach shows that Dempsey's private secretary specifically requested use of the €7,890-an-hour Gulfstream IV.

"Permission is requested for the use of the Gulf Stream Jet [sic] to enable the minister for transport, Mr Noel Dempsey, to travel from Derry to London for a meeting that he will be having [deleted] on Tuesday morning," it said.

"The minister intends travelling from Derry on Monday evening 19 July returning to Dublin on Tuesday 20 July... I have contacted executive branch and the Gulf Stream Jet is available, subject of course to the Taoiseach's approval."

Further documents say the possibility of "commercial options" on board regular scheduled flights was investigated but ruled out.