Tree planting in Oxford has been reduced following a dispute between the city and county councils over highway maintenance costs.

Cllr Craig Simmons with daughter Beri, three, and fellow Greens Mary-Jane Sareva, left, and Beri's mother Elise Benjamin in Oxford's High Street

Green councillor Craig Simmons has called for 100 new trees to be planted in the city centre to tackle air pollution.

He backed a campaign by the charity, Trees For Cities, which is planting trees in cities as they filter out harmful vehicle emissions such as nitrogen dioxide.

A dispute between the city and county councils over money for the maintenance of major roads has prevented a number of trees from being planted over the past six months.

Instead of 50 new trees being planted on major routes in that time, there have been only 10.

Jean Fooks, Liberal Democrat city and county councillor, said: "The county pays the city for doing maintenance work on certain highways and that covers tree planting.

"The city says the county is not paying them enough money to do the job at the moment. As a result, we have missed an entire planting season.

"It's an excellent idea to plant new trees as a method of reducing pollution."

Susanna Pressel, Labour city councillor and a member of Forest of Oxford, which campaigns for more street trees, said: "It's horrible when a tree dies and you can't replace it."

David Robertson, the county council's executive member for transport, said: "Negotiations are continuing and I'm sure there will be an amicable settlement soon. The more trees the better."

Dr Sharon Cosgrove, the city council's director for the physical environment, said: "The city council has been subsidising the cost of tree maintenance work along major highways for a number of years - which is legally the county's responsibility.

"The county pays £22,000 each year, but there is a shortfall. We are talking about how this work is funded in the future and looking to formalise the tree maintenance agreement and upgrade the budget.

"I am confident this issue will be resolved soon but, until contracts are in place, the city council has to limit tree plantings along highways. All pruning and tree safety work is being carried out and the city council is still planting plenty of new trees across the city."

The city and county council have agreed to investigate measures to reduce nitrogen dioxide levels, which are twice Government limits in some streets, including Queen Street, but so far these have not included tree planting.

George Street, High Street and Park End Street also exceed the nitrogen dioxide target of 40 micrograms per cubic metre, which needs to be achieved by 2005.

Mr Simmons renewed calls for trees to be planted in Cornmarket Street and Bonn Square, where there are plans for it to be re-landscaped.

Police objected to trees in Cornmarket because they would obscure CCTV cameras.