More than 20 MPs broke Commons rules by failing fully to declare luxury trips paid for by foreign governments, it was claimed today.
The politicians visited famous holiday destinations such as the Maldives, Cayman Islands, British Virgin Islands, Mauritius, Gibraltar and Cyprus, according to research by the BBC.
However, on many occasions they failed to mention the hospitality received when tabling questions and participating in Parliamentary debates.
Labour MP Andrew Dismore, a member of the Standards and Privileges Committee, is alleged to have breached the regulations it enforces more than 90 times in relation to annual trips to Cyprus.
Tory MP David Amess is said to have called a debate on the Maldives in 2007, telling the House that his "splendid visit" had given him "an early taste of paradise".
He apparently suggested that the UK Government "could be encouraged to do a little more than is being done at the moment" for the tiny nation.
However, despite tabling 15 questions and leading two debates, at no point did he declare his interest as required, the BBC claimed.
Shadow defence secretary Liam Fox admitted breaching rules twice in asking parliamentary questions after visiting Sri Lanka.
He said one trip from 2007 was initially not recorded properly due to a staffing error, but later added to his register entry.
"I do however recognise that when asking one question in 2008, I should have noted an interest and the Registrar has been informed of this," he added.
Liberal Democrat frontbencher Norman Baker allegedly broke regulations 37 times, leading debates and tabling questions about Tibet.
He travelled to India twice courtesy of the Tibet Society and the Tibet government-in-exile, the BBC said.
Under Commons rules, MPs are not allowed to press for UK government assistance to a place from which they have recently received hospitality. They must register the trip and then declare relevant trips when tabling questions, motions or debates.
In total, the BBC identified some 400 breaches by comparing the overseas visits registered by MPs with their activities in parliament.
MPs highlighted in the probe have denied their behaviour amounted to lobbying on behalf of a foreign power. Many apparently blamed administrative errors, or pointed out that they had declared the interests on numerous other occasions.
Mr Dismore, Mr Amess and Mr Baker were not immediately available for comment when contacted by the Press Association.
The chairman of the Commons Public Administration Select Committee, Tony Wright, told the BBC the alleged failures were "very serious" and "unacceptable".
"If rules are being broken they need to be adhered to and it's as simple as that", he said. "If that means taking some action we should do that."
He went on: "There should be a system in place to control this kind of thing, to stop abuses, and to make sure there's transparency.
"That's what we really need. If that's not working then it ought to and people in charge of that system ought to ensure that it is working."
In a statement, Mr Dismore accused the BBC of misconstruing the rules and failing to understand the situation in Cyprus.
"The Cyprus problem is complex and the various administrations and interests on the island are very separate from each other, as demonstrated by the protracted negotiations between the leaders of the two communities to attempt a reunification settlement," he said.
"The BBC have confused visits undertaken with one Cypriot administration, the Republic of Cyprus parliament in the south, with points raised about others such as the UN administration in the buffer zone or the Turkish administration in the north."
He went on: "I have a large Cypriot community in my constituency for whom the Cyprus issue is of great importance.
"There was no personal advantage to me either financial or in kind from my work on Cyprus or from the study visits.
"All visits were correctly registered with the Registrar of Members Interests within the required timescale.
"When I spoke in the House I made the required declarations of interest at the start of my speeches.
"There is no suggestion of financial impropriety. There is no suggestion of misuse of public funds."
Sir Stuart Bell, a Labour backbencher who sits on the ruling House of Commons Commission, said the claims further tarnished the reputations of MPs.
He described it as "a further error of judgment in our colleagues".
"Twenty of them, which unfortunately means 646 MPs are now tarred with the same brush," he told BBC Radio 4's Today programme.