The Labour Party is urging the Government to pick up the Pay Equality Bill put forward by the Human Rights Commission.
The bill would end confidentiality agreements in contracts, meaning a woman doing the same work as a man would be entitled to know what he was paid.
The Government has so far showed little interest in the legislation.
In Question Time in Parliament on Thursday, Labour MP Carol Beamont asked about the difficulties for women to make pay discrimination claims.
Ms Beaumont asked if the fact very few cases have been taken shows that there are very few issues, or that the existing legislation is not adequate to deal with the problem.
Deputy Prime Minister Bill English replied that it is also possible that employees and employers follow the law which says people cannot be paid differently based on their gender.