Published Wednesday, 13 May 2009
Lady Sylvia Hermon's decision comes after the party announced it had merged with the Conservatives.
In an interview with our political editor Ken Reid the North Down MP said: "I'm not a Tory, never have been and never will be."
The Ulster Unionists are fighting the European elections in around three weeks time under the Conservative and Unionist flag.
Responding to the comments from Lady Sylvia Hermon MP Sir Reg Empey said:
"The leadership of the Ulster Unionist Party is disappointed that Lady Hermon, in the middle of an election campaign, has chosen to give a series of interviews in which she has challenged Party policy and the collective decisions taken by her colleagues."
The statement went on to say that Lady Hermon was assured last year that she would not be required to take the Conservative Party whip in the lifetime of the present Parliament.
Expenses
Earlier Lady Hermon revealed she has paid back more than £2,700 in Parliamentary expenses which she over-claimed for rent on a London flat between 2005 and 2006.
The Ulster Unionist MP said she was "profoundly upset and embarrassed" but also angry that the House of Commons Fees Office did not draw her attention to her mistakes at the time.
Lady Sylvia, widow of former RUC chief constable Sir Jack Hermon who died last November after a lengthy battle with Alzheimer's disease, had believed all her claims were above board.
She said she was well aware of the public mood and shared the very real sense of outrage over revelations in recent days about "the most outrageous expenses claims by MPs".
Lady Sylvia said: "I've never bought property nor had a mortgage in London; I didn't have a television at any stage, didn't watch DVDs of any nature, didn't claim for food in London, furnishings, security or cleaning, didn't claim for dog food, chandeliers or for any other weird and exotic items."
'No excuses'
She said when she was elected in 2001 she rented a small one-bedroom flat about 20 minutes walk from the House of Commons, three years later swapping it for another slightly nearer.
But when her husband was admitted to hospital early last year she ended the tenancy and since then had no second home, choosing instead to spend as much time with Sir Jack as possible and to stay occasionally in a hotel when there was a crucial late night vote.
Therefore her only claims were rent, council tax, telephone and electricity for the flats, she said.
"Straightforward , I thought, until Monday last, when I phoned the Fees Office only to discover it had overpaid me for two months rent between 2005-6.
"Even though I immediately reimbursed the House of Commons with the £2,730, I remain profoundly upset and embarrassed.
"I'm also very angry that the Fees Office did not draw my attention to my mistakes at the time, especially as I had on various occasions specifically written on claim forms that I wanted them to be checked."
But the North Down MP also said: "There can, however, be no excuses. The mistakes were mine, which I have rectified and for which I am extremely sorry."