Most voters agree that there is little that is more important than family.

And yet for the last two decades governments have consistently failed to reform a tax system that benefits single people over married couples with children.

In real terms the tax threshold has scarcely risen for families, while it has risen significantly for single people without family responsibilities.

The tax burden on families has increased, especially where tax credits have not been available.

Where tax credits have been paid, marginal tax rates are extremely high.

The bias against single-earner families is particularly severe, with there being a significant financial disincentive for parents to stay at home to raise children.

The importance of marriage and family to our children’s well being needs to be recognised.

George Osborne’s latest Budget was hailed as a triumph, with its once in a generation shake-up of pensions, its raft of business-supporting measures and the welfare cap.

However, while the Budget was positive overall, there was little for low-earning families to cheer about.

There is an opportunity for the Conservative Party to correct this iniquity.

In a year’s time there will be another Budget, with a general election following soon after. The Chancellor must use his final Budget of this Parliament to rebalance the tax system and remove the bias against families.

The problem results from a change in the tax system, made in 1990, under which people are taxed as individuals instead of as family units.

The intention was that if either a wife or a husband were not able to make full use of their tax free allowance then the unused portion could be transferred to their partner.

Regrettably, the transferable allowance was never introduced, and the measures that were introduced instead were insufficient. In any event they have since been withdrawn.

As a result there is currently no recognition of marriage in the tax system, and the decision for one parent to stay at home to raise children has become extremely financially difficult, and is becoming more so with the soaring costs of childcare.

Marriage, it should be remembered, is a powerful force of social cohesion and stability.

The research conducted in this area suggests that there are considerable advantages to marriage.

Families where the parents are married are, on the whole, healthier, wealthier, and more stable.

A prominent US study concluded that: “Marriage is an important social good, associated with an impressively broad array of positive outcomes for children and adults alike.”

The evidence to support this conclusion is convincing. Children whose parents marry and stay married have lower rates of alcohol and drug abuse.

Children of married parents score higher on measures of academic achievement, and are more likely to gain qualifications.

Children from married families are considerably more likely to have some level of qualifications by the time they were 30 years old.

Boys raised in lone-parent homes are about twice as likely (and boys raised in step-families are three times as likely) to have been imprisoned by the time they are 30.

A report published in 2010 by the Institute for Fiscal Studies also highlighted differences between children living with married parents and with children living in cohabiting families or with single parents.

The results were stark: by the time children are aged three, there are already significant differences in child outcomes between children born to married parents and those not.

On average, children born to married parents display better social and emotional development and stronger cognitive development than children born to cohabiting parents.

The most negative outcomes for children tend to be from single parent households.

And yet despite the evidence the Government offers no support to families.

Families are paying a greater share of income tax than they were 20 years ago. Tax credits have left families reliant on handouts from the State.

This is a trend which Iain Duncan Smith has expended considerable energy on trying to reverse.

In addition, the marginal rates that some families face are so severe, over 70 per cent in some instances, that when a family’s income grows to around £20,000 per year rather than the minimum wage of around £12,000, they have little more after tax than when they were on the minimum wage.

This produces a disincentive to aspiration.

The Conservatives are beginning to address the problem and, better late than never, last year this Government confirmed that it will bring in a transferable marriage tax allowance worth up to £200 for some families.

This policy should be taken far further.

The Conservatives should pledge to increase the transferable amount until the entire tax-free allowance, raised to £10,500 in the last Budget, is transferable, as should have happened when the taxation system was changed almost a quarter of a century ago.

This offers proper support to those families that need it.  It would be an expensive policy, but we should declare it as a long-term aim of our tax policy, explicitly designed to help and support stable families.

Furthermore, by making the tax-free allowance fully transferable one-earner marriage would be recognised in the tax system.

It cannot be right that the tax burden on single people has fallen while the income tax burden on some families has remained broadly the same.

When the personal allowance is fully transferable – and it will take many years – the state will be truly neutral on family decisions about whether parents go out to work or stay at home.

That decision will then be made by the people best qualified to make it, the parents themselves.