The campaign to rezone Surbiton and Kingston stations took a further step this week with MP Edward Davey writing to the London mayoral candidates to ask for their support.

Writing to the Mayor of London Ken Livingstone and Conservative mayoral candidate Boris Johnson, Mr Davey said: "As a result of being allocated to zone six despite being a zone five distance, Kingston and Surbiton stations saw single and day return ticket prices rise by over 35 per cent.

This is set to get much worse from January 2010, when seasonal tickets from Kingston and Surbiton will move to zonal pricing - so we could see increases of between £400 and £500 in annual rail tickets."

Information about the price hike for commuters was revealed to Mr Davey through a series of Freedom of Information requests. It has provided more weight to his campaign to rezone the stations, which began when the initial zonal pricing was introduced.

The move to rezone a station is not without precedent - Cheam and Belmont were moved from zone six to zone five in January 2005, and Stoneleigh was rezoned in January 2007.

The re-zoning of the stations has received the initial backing of Transport for London so the next step in Mr Davey's campaign is to win the support of Transport Secretary Ruth Kelly and South West Trains.

He believes that by getting support from the next London mayor more pressure will be put on the Government and train operator to change the zones.

Writing to the candidates, Mr Davey told them he already had the backing of the Liberal Democrat mayoral candidate Brian Paddick, and said: "This should not be a party political matter, so I am writing to other London mayoral candidates to ask them to support my campaign."