Oxford City Council is set to have its first Conservative councillors since 2002.

Paul Sargent and Tia MacGregor are tomorrow set to complete their move from the Liberal Democrats - via the Independent group - to the Conservative Party.

Witney MP and party leader David Cameron was scheduled to appear at a press conference at Oxford Town Hall to announce the switch.

The Tories have had no representation in the city for several years, but the true test will come next year when the pair are up for election in their respective Quarry & Risinghurst and Carfax seats.

Until then they are the smallest group on the council.

In a move plotted since the New Year, the duo said they hoped to kick-start a Tory revival in Oxford, but now face the prospect of a backlash from some of their constituents who voted for them when they represented the Liberal Democrats.

The pair said they did not quit the council and call a by-election because of the cost to the taxpayer.

When Dr MacGregor, 39, quit the Lib Dems earlier this year she said the party "was no longer working for her".

She went to join Mr Sargent, who quit the party in May 2006 after he failed to get a seat on the authority's decision-making executive, as an independent When he quit the party he said "I still share many of the principles and policies of the Liberal Democrats, but sometimes you have to go in a different direction."

It is unclear whether the pair would vote with the Liberal Democrat group.

Last night Dr MacGregor said: "It is something I have been thinking about for some time.

"I am impressed with their policies and on a personal level their views on the NHS.

"Becoming an independent was bad enough in some people's eyes.

"So far no one has said anything negative, but I am sure there will be people who are not happy with my decision to join the Conservatives when they voted for a Liberal Democrat."

The Tories wanted to capitalise on the double defection by announcing it at the time of this month's local elections, but were told to hold off.

Rumours of a switch first surfaced after Dr MacGregor and Mr Sargent were spotted touring the city council with Tory county council leader Keith Mitchell earlier this year.

Mr Sargent said: "I thought about it carefully and decided I needed to be part of a larger political party."

The switch makes hardly any difference to the political make-up of the city council, which has 48 members.

Labour is still the largest group with 18 councillors, the ruling Liberal Democrat group has 16, the Green group has eight and the Independent Working Class Association has four.

Defections are nothing new at the Town Hall.

Sarah Margetts left Labour to become an independent in January, 2002; Mick McAndrews switched from Lib Dem to Labour in May, 2000; and Bob Hoyle left Labour to join the Lib Dems in April the same year.

And nationally, former Witney MP Shaun Woodward quit the Tories to join Labour, while Robert Jackson, Ed Vaizey's predecessor in Wantage, went the other way.