Two top Liberal Democrat politicians brought their General Election 'battle bus' to Bradford today to hear for themselves the plight of a small engineering business which could not get a bank loan to invest in new machinery.

Party leader Nick Clegg and treasury spokesman Vince Cable came to the city to support their candidate, Bradford councillor David Ward, in the new Bradford East seat where the Lib Dems are confident of unseating sitting Labour MP Terry Rooney.

They visited Printing Roller Services in Caledonia Street, a six-man firm that refurbishes parts for printing machinery. The Lib Dems chose the company, whose bank turned down a request for funding for a new £30,000 machine from the US, to push their call for reform of the banks Nick Clegg has unveiled tough new plans to ban loss-making banks from paying discretionary bonuses.

Mr Clegg said: "Bankers must understand that after the billions pumped into the banking sector, there can be no financial or moral justifications for the obscene bonuses which are still being paid out.

"That is why we are unveiling five key proposals to bring the bonus culture in banking under control. There must never again be rewards for failure. It's simple: if you're not making money, you shouldn't have a bonus. That's just common sense."

The Liberal Democrats also pledged "the most radical change in taxation in generations" which would cut tax bills for millions of people by £700 a year. The flagship "tax switch" policy to increase the personal allowance to £10,000 per person will cost £16.8 billion.

Nick Clegg said it would be paid for by closing loopholes exploited by the rich, cracking down on tax avoidance, introducing a new mansion tax on homes valued at more than £2 million and increasing aviation duties.

Mr Clegg said Labour had "ducked doing anything meaningful" on bankers' bonuses and he would "put money on the Conservatives doing exactly the same".

Nick Clegg was greeted by a small band of party workers and well-wishers and presented with flowers by four-year-old Naina Kains, whose grandfather runs a nearby firm making hospital mattresses.