Anybody worth more than £1 million faces coming under scrutiny from inspectors in a fresh crackdown on tax avoidance announced by Liberal Democrat Treasury Chief Secretary Danny Alexander.

The move will mean 200,000 more people will be targeted by HM Revenue and Customs' affluence unit, set up originally to study the affairs of the 300,000 with assets and property of more than £2.5 million.

Mr Alexander, speaking to the Mail on Sunday at the start of the Lib Dems' annual conference in Brighton, said officials would "sniff out" anybody who was not paying their fair share of tax.

"The measure will apply to people with homes and assets of more than £1 million," he said. "The wealthiest did best in the boom years and it is right they should pay more now."

Mr Alexander said the affluence unit, boosted from 200 to 300 staff, would cross-reference files and records to spot signs of avoidance. "They will look at anomalies and sniff out any problems," he said.

A new coalition drive to hit the rich will also include separate moves to stop high-earning BBC personalities from using tax avoidance schemes and fines for tax-dodging footballers.

The initiatives are likely to play well with Lib Dem activists and come as Deputy Prime Minister and Lib Dem leader Nick Clegg vowed to play hardball with David Cameron over the future of the coalition.

Meanwhile, Energy Secretary Ed Davey will on Sunday intensify the battle with Chancellor George Osborne over green measures by backing calls for a target on cutting energy sector emissions by 2030.

And Mr Clegg admitted at an opening night conference rally that the Lib Dems had made mistakes during their first two years in coalition.

But he stressed it was only "half-time" in the coalition's term of office and rubbished suggestions he would step down before 2015 by promising to fight for the party's values right up to the general election.