Wealthy fathers who fail to pay generous child maintenance to their ex-wives risk having their shares and property portfolios plundered by the government.

Under the plans, mothers who successfully claim they deserve more money for child support will also be able to claim a share in any profits their ex-partners make from selling assets – even those acquired long after the divorce. And authority will be given to civil servants to raid the father’s bank account and withdraw lump sums.

Lawyers warn that the new organisation to replace the much-criticised Child Support Agency (CSA) is also likely to face disarray as fathers challenge it on human rights grounds.

Kim Fellowes, a family law expert who has briefed MPs, said: “Ministers are rubbing their hands in glee because these extraordinary new powers have gone through on the nod, but when they come into force, there will be chaos. There will be endless appeals.”

The CSA is being axed after failing to recover £3.5 billion from errant parents, the majority of them fathers. The new agency, The Child Maintenance and Enforcement Commission (CMEC), is to be far tougher and will be given powers to take payments directly from wage packets.

The new laws will also give officials powers to impose “lump sum deduction orders” – to take money from bank accounts and intercept money fathers make from selling a house or flat before it even reaches their bank. Fellowes, who chairs the child support committee at Resolution, the 5,000-strong body of family lawyers, said: “The plans are a mess.”

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