New road signs to deter motorists from straying into town centre bus lanes could hit people hard in the pocket, it is being claimed.

MP Mike Martin says the proposed blue circular boards “imply permission” for drivers to enter a zone where they could be fined up to £70.

He has invited Kent County Council (KCC) highways bosses to walk the route in Tunbridge Wells town centre to explain his concerns and those of the local council, residents and road users.

They argue red circle signs elsewhere in the town are a more effective deterrent.

In a letter to Cllr Neil Baker, the KCC highways chief, Mr Martin said: “Together with Tunbridge Wells Borough Council (TWBC), residents have repeatedly raised issues to KCC.

“So far, these complaints and suggestions have fallen on deaf ears. In our view, the changes proposed in the consultation…will make the situation worse as the proposed blue signage…is unclear to motorists.

“Blue signs imply permission but the main message of the sign is that going through the traffic scheme is forbidden.”

The Liberal Democrat MP for Tunbridge Wells, who won his seat at the general election last July, argued there are red circular signs elsewhere in the town centre and should be used in bus lanes near the war memorial at Mount Pleasant.

Mr Martin’s letter added: “We would like to invite you (Cllr Baker) to Tunbridge Wells to walk around the scheme at your earliest convenience, with a view to jointly commissioning an independent traffic expert to propose solutions. This would be funded by the borough council.

“Whilst this is happening, we would ask that you postpone the planned changes which will, in our view, worsen the situation, not improve it.”

The traffic scheme has been in place for around two years and has been administered by TWBC. Nearly 12,000 fines were issued in the past 12 months with a possible £840,000 in fines although the amount collected is likely to have been substantially lower due to early payments, non-payers and appeals.

Under the current review, Kent County Council will take over the administration of, and income from, the scheme in future but Cllr Baker insists the scheme aims to change driver behaviour, not to raise money.

The blue signs are part of its standardisation of the network in Kent and are in line with the Highway Code.

Shoppers in the town seemed to agree with Mr Martin’s assessment when shown photos of the red signs and the new blue ones.

Sue Callaghan, who lives locally, was fined after being caught out driving through an existing blue sign elsewhere in Tunbridge Wells.

She said: “It wasn’t until afterwards and I had the fine and the letter that I saw the signs. Why is it a blue circle? It makes more sense to have a red circle.”

Guy Watson, of Rochester, said: “To me the red sign is more obvious and the blue one doesn’t say no cars, so some people would be confused.”

A KCC statement said: “As the local highways authority, we need to ensure all Moving Traffic Enforcement sites across Kent are in line with legislation. Changing the signage in Tunbridge Wells to blue signs complies with the Department for Transport guidance, and means our approach is consistent across Kent - the same blue signs are already in use at other active enforcement locations in Ashford, Dartford, Dover and Gravesend.

“We understand concerns the new signs will be blue rather than red, however, these signs are compliant with the Highway Code.

“A warning period is in place for six months at the new sites to ensure all motorists are aware of the restriction and can plan another route in future to avoid receiving a penalty charge notice.”

KCC explained a motorist will be allowed one contravention but will be fined £70 thereafter, but halved if paid within 21 days. There is no fixed start date for the new enforcement.

The council said: “Following government legislation, we are obliged to issue a warning notice to the driver for their first offence during the first six months that the site becomes live. The notice sets out that any further contravention will result in a penalty charge notice being issued.”

KCC’s chairman of the environment and transport committee, Cllr Sean Holden, himself a former Tunbridge Wells borough councillor, said: “All the noises the Liberal Democrats are making are covering up the fact they fined thousands of people for simply making a mistake.

“It has just been a revenue raising lark and have been pretty unrepentant about it.”