The Chancellor has announced a marriage tax break worth up to £200 a year in his Autumn Statement last week.
The measure applies to married couples where both are basic rate tax payers, and where one spouse earns less than the personal tax allowance.
The Government wants it to be introduced in April 2015 – a month before the next general election.
George Osborne said the tax allowance will benefit four million families, “many of them among the poorest working families in our country”.
But Harry Benson of the Marriage Foundation previously said the measure is “political game playing”.
He said: “A small tax break from government will never be enough. It can only be the beginning. It’s a flag in the ground.”
“The real disgrace is that we have turned our backs on marriage for far too long. It has cost us dear”, he added.
Former Tory Chancellor Nigel Lawson has said the marriage tax allowance should be more generous and introduced sooner.
“I think it should be up and running during the lifetime of this Parliament”, he explained.
“It makes it easier to reverse it if it’s not up and running because you’re not taking anything away from people that they already have”, he added.
A group of faith leaders and campaigners, including Bishop Nazir-Ali and Lord Singh, called for the tax break to be meaningful.
The tax allowance could be seen as an “empty gesture” and should be paid at a much higher rate, they added.
Last week, the Prime Minister said that he sees the marriage tax break as something he would like to “extend further”.
Writing in the Daily Mail in October, the Prime Minister said he is not trying to bribe people to get married.
“This policy isn’t about the money but about the message that people who make a lasting commitment should be recognised in some way”, he said.
“All we’re saying is that marriage is a good thing for our country – it’s the ultimate form of commitment under the law – and we want to show our support for it”, he added.
But critics say the move discriminates against non-traditional families.
“The government’s claim that we’re all in this together rings increasingly hollow as single parent and many couple families are excluded from a marriage tax break that will cost hundreds of millions of pounds”, said Fiona Weir, chief executive of Gingerbread, a charity for single parents.