Faith leaders have said that a marriage tax break of £150 is too low.
The measure is due to come into effect in 2015 but the faith leaders argue that the allowance should be "in the thousands" if it is to have any impact on the rate of family breakdown.
They said that the Government should make the tax break more generous if it does not want it to be "dismissed as an empty gesture".
Signatories of the letter include Bishop of Chester, the Right Reverend Peter Forster, former Bishop of Rochester, the Right Reverend Michael Nazir-Ali, director of the Network of Sikh Organisations, Lord Singh, and former general secretary of the Muslim Council of Britain Sir Iqbal Sacranie.
The letter states: "Family breakdown costs the taxpayer an estimated £46 billion a year.
"It is therefore clearly in the interests of government and the taxpayer to work to counter the devastating trend of family breakdown and backing marriage in the tax system is a sensible first step.
"This is why we urge all political parties to back the new transferable tax allowance and go further by ensuring that it cannot be dismissed as an empty gesture, because it has been set at the low level of £150.
"To be meaningful it must be paid at a higher rate even if this meant a phased introduction or application of other conditions. "