I have just helped the United Kingdom Independence Party (Ukip). I have jumped ship. It is a small party whose main wish at the moment seems to be a desire to become even smaller; so I did my bit and resigned.

Why now? Surely Ukip was on the verge of a great political breakthrough? After the 2004 European Elections, Ukip was on the crest of a wave with 12 Members of the European Parliament (MEPs), 2.7 million votes, 16.8 per cent of the vote and membership of 26,000. But now, as the next round of Euro elections approaches, the great breakthrough has turned into break-up.

Ukip's 12 European parliamentarians have, by defection and expulsion, dropped to nine – and one has even left his constituency to live elsewhere, without telling his constituents. At the Henley by-election last year, the party finished sixth, behind both the Greens and the BNP with just 2.4 per cent of the vote, and membership is down to 14,000 (sorry, make that 13,999) and on the slide. To make matters worse there are accusations of rigged internal elections, tales of extravagance and high living in Brussels and an embarrassing stampede to try to board the European gravy train this June. In short, Ukip is in the process of imploding.

I have absolutely no personal political ambition whatsoever. For me the summer was going to involve seeing gorillas in the Congo for Telegraph Weekend and visiting St Kilda for the first time. I was encouraged to stand because of my concern about the state of my country and I reluctantly agreed. Because of a farcical series of accidents, health problems and other commitments, I had a special dispensation to submit my papers a few days late. Or at least I thought I had.

When I contacted the officials as arranged they told me I was out of time. So I phoned Nigel Farage, Ukip's Blair-like, ex-public school leader, who said he was very sorry and would do his best to sort things out, but "it'll be up to the Political Committee". He came back later with bad news. "The Political Committee won't accept your late documents. I'm really sorry." I have since found out that Mr Farage is Ukip's Political Committee. It runs at his whim with no obvious agenda or minutes. Piers Merchant, a former Tory MP who is now Ukip's Returning Officer, informed me that the process was "flawed" and that there should be a re-run. But there has been no re-run and Ukip refuses to send me a copy of the Returning Officer's report even after a Data Protection Act request.

It seems that Nigel Farage has managed to obtain almost complete centralised power of Ukip. Other late nominations were apparently accepted, some people heading MEP lists have been forced out to be replaced by others and three members of Ukip's National Executive Council were expelled for criticising the leader. Other high-profile Ukip members have also been removed over the years, so as not to threaten Farage's control or image. The party's own policies – such as opposition to GM crops – have been reversed without the membership knowing, including me. Stories from Brussels suggest that Ukip's MEPs have come to love the high life of gravy and status. The party created to fight centralised government, sleaze and corruption has become a mirror image of the body it professes to loathe. The grassroots of Ukip are good people, but their party has been stolen from them by their executive; and with David Cameron seemingly afraid to say the word "Europe", they have nowhere to go – unless lured by the false smile of the BNP.

Just under 2,000 years ago Tacitus wrote words to the effect: "Britons are very good at being Roman. They like the baths, the forum and they think they are becoming Roman whereas in fact these devices enslave them to Rome." Replace Britons with "Ukip MEPs", and Roman with "European", and the disintegration of Ukip is explained.