The chief secretary to the Treasury will pledge to get more from “the small minority of wealthy people who don’t play by the rules”.

The BBC reported the Lib Dems want to raise £9bn by tackling tax avoidance by 2015.

The report said the number of HM Revenue & Customs (HMRC) staff dealing with tax-evasion in Liechtenstein will be doubled to target those “hiding” assets offshore.

Alexander announced £900m in extra resources for HMRC at the party’s conference last year. Today he will say the UK is making “good progress” and “we should all be proud of it”.

“Fair taxes in tough times means everyone playing by the same rule book, and everyone paying their fair share”, he will add.