Oxford Greens have threatened to pull out of a power-sharing deal on the city council after Liberal Democrats formed a new county alliance with the Conservatives.

They have written to Margaret Godden, leader of the county Lib Dems, expressing their "extreme concern" at her decision to join forces with the Tories at County Hall.

The Tories and Lib Dems will control the new county council executive, with Labour filling the role of opposition.

But the Greens, which have run the city council with the Lib Dems since Labour's defeat in May 2000, say they fear their partners' ability to control "the more reactionary tendencies" of the county Tories.

The Greens' representatives, Paul Ingram and Craig Simmons, have told Mrs Godden that the Conservative dominance in the county could have a significant impact on the city, where their own partnership with the Democrats could suffer.

The two councillors say the Greens would "vigorously oppose any watering down" of the Oxford Transport Strategy.

Cllrs Ingram and Simmons claim county politicians lack commitment to transport policies, and say they are "appalled" at the decision to restore parking spaces in Broad Street and at the idea of relaxing restrictions in High Street.

They add: "If there is further significant weakening of the OTS, we would have to reconsider our position within the administration of the city council.

"Up until now, we have engaged positively with the Liberal Democrats to tackle the many problems left over from the previous Labour administration without any threats of withdrawal.

"But there are limits, and we cannot sit by and continue in this arrangement if your party is so clearly implicated in any retrograde steps in an area which is so fundamental to the quality of life of Oxford's residents."

The Greens are seeking a meeting with Lib Dems at both city and county level to discuss the new alliance with the Tories and to express their concerns in more detail.