Lord Digby Jones also predicted that shadow chancellor Ed Balls would raise the rate to 55p or even 60p once in power.
Another former minister, Lord Adonis, said restoring the 50p rate was necessary to ensure all parts of society made a "fair contribution" to reducing the deficit.
The comments came as Mr Balls defended his pledge to bring in the higher tax rate to pay down the UK's Budget deficit. He ruled out raising the rate past 50p.
And he insisted it would stay in place only as along as it took to get the UK's finances back in the black.
Mr Balls also hit out at attacks that the plan was anti-business.
A poll overnight suggested the policy was also extremely popular with the public.
Labour introduced the 50p top rate of tax before it lost the 2010 General Election.
The rate was reduced to 45p by George Osborne.
Lord Jones, a former business minister who also served as director general of the Confederation of British Industry, said Labour's current economic policy appeared to be "if it creates wealth let's kick it".
lLabour will today announce plans to create a US-style Small Business Administration to work across government to remove blockages to business development.
Shadow Business Secretary Chuka Umunna MP said such a body would: "create a step change in the opportunities for small businesses from government procurement."