Tory leader David Cameron popped into a Witney business to hear the owner's complaints about tax and transport.

The visit was in response to a letter from Brendon Cross, managing director of STL Communications, who had asked for help in sorting out a wrangle with tax authorities over the sale of part of his business.

Having set up his company in 1995, after British Telecom was privatised, eight years later he had built it up to 80 employees and was approached by Carphone Warehouse, which wanted to buy his fixed lines and calls business for £6m.

The sale went through in 2004, but the tax question has still not been settled, Mr Cross told the Witney MP.

Finance director Bill Smith explained that because of a technicality — Carphone Warehouse had bought the assets of the company rather than the actual business — the sale had been treated differently for tax purposes.

Mr Cameron was sympathetic. "My wife has sold a business and now she has another one.

"Her whole life plan is based on flogging the business." He added: "The growth of the economy is going to be coming from small businesses like yours, not from the big companies, which are laying people off. We have to have a tax system that allows an exit for entrepreneurs, which encourages people like you to take the risk of setting up a business."

Mr Cameron promised to write to HM Customs & Revenue, but he was cautious about making concrete promises to lower taxes on small businesses, or changing the system in a way that might open loopholes.

"There is no money in the locker, so we cannot promise to restore the 10 per cent taper on corporation tax, but we have to find something to encourage enterprise."

On transport, he said there were no magic answers to road congestion and the problems at Heathrow. Mr Cross said a high-speed rail service was needed connecting London and Birmingham.

Mr Cameron said: "If you watch our conference, you might learn something interesting about that."