MPs have overturned controversial Lords amendments which have threatened to scupper the government's Civil Partnership Bill.

Peers had heavily altered the legislation, which aims to outlaw discrimination in areas such as inheritance, tax allowances and next of kin status, when it passed through the upper house in June.

Conservatives in the Lords put forward plans to give groups including carers and family members the same inheritance rights as the new "civil partners".

But ministers described the move as "unworkable" and overturned the changes using the government majority in the Commons, while critics accused the Lords of seeking to bring the bill down because of an anti-gay agenda.

Equalities minister Jacqui Smith said the Lords had put down "wrecking amendments".

"Of course we recognise that there are genuine concerns about the needs of carers," she said.

"But this bill is entirely the wrong place to deal with these concerns."

While Michael Howard has given his MPs a free vote on the issue, openly gay Tory frontbencher Alan Duncan spoke out in favour of the reforms.

However, highlighting rifts within the Conservative ranks, former Home Office minister Ann Widdecombe said the bill "undermines the uniqueness of marriage".

Support

Speaking in the debate, Smith said the bill "has widespread support... from across the political spectrum".

"It is a crucial step to a fair and civil society and I look forward to this House returning it to its intended form," the minister said.

Tuesday's second reading debate returned the plans to their original form and sent them back to the Lords.

However because the bill was introduced in the second chamber the Parliament Act cannot be invoked to enforce the will of MPs.

With the end of the Westminster session approaching, time could be short for the legislation to "ping pong" between the houses in search of a compromise.

The bill proposes to grant formal recognition of long term homosexual partnerships in response to years of lobbying from gay rights groups.

Couples who registered would have a new legal status as civil partners and would, according to the government, "acquire a package of rights and responsibilities".

The scheme will not apply to heterosexual cohabitees on the grounds that they have the option of civil or religious marriage denied to homosexuals.