The Deputy Prime Minister Nick Clegg has previously ridiculed the idea of a tax break for married couples as "patronising drivel that belong in the Edwardian age".
The coalition agreement spells out that Liberal Democrat MPs can abstain on a plan to recognise marriage in the tax system.
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Commuters were also warned to expect travel chaos as Doris gathered speeds of nearly 90mph.
A man with 62 penalty points on his licence is among thousands of motorists allowed to drive despite exceeding the limit warranting a ban.
Storm Doris is set to bring severe weather across much of the UK on Thursday as heavy rain and strong winds push in from the west.