The Northern Ireland Assembly has voted against the health minister's decision to locate maternity services at the Royal Victoria Hospital in Belfast.

Members voted 53 to 37 in favour of a motion from the Democratic Unionist Party's Iris Robinson endorsing the decision of the executive's health committee which favoured building a new maternity unit at Belfast City Hospital.

The Assembly decision is unlikely to have any effect, however, and there is speculation that campaigners for the City Hospital may launch a legal challenge.

Women's Coalition assembly member for the area, Monica McWilliams, has criticised the legislature's lack of power to overturn the minister's decision.

"It has to make a difference or otherwise we may not have an assembly or a health committee," she said.

The decision by the assembly has been welcomed by the Jubilee Action Group who urged the minister to change her decision.

A spokesperson said the main argument to locate the maternity unit near the children's hospital in the Royal complex was "spurious".

"It was very pleasing to see that many assembly members could see the advantages of the city site," she said.

The debate over where maternity services should be sited has raged since 1996 and centred on the government's intention to establish one unit at either the Royal Victoria Hospital or Belfast City Hospital.

The minister said she hoped the new maternity hospital would be in place in five to six years time but, in the interim, combined maternity services would be located at the refurbished Royal Maternity Hospital in west Belfast.

She said her decision was based solely on "what was best for women, mothers and babies".

It is thought that the Jubilee maternity unit will be demolished to make way for the building of a new cancer centre for the province.