By Carolyn Dempster BBC, Johannesburg

South Africa's ruling African National Congress has gained control of Western Cape province, following the defection of two MPs.

Mbeki's party now has control of all but one province

The shift in political power was made possible by new floor crossing legislation which allows politicians to defect to opposition parties.

The law which effectively came into force last Friday gives politicians 15 days from that date to switch parties without losing their seat.

Since Friday, three New National Party members and one from the United Democratic Movement have joined the ANC in the Western Cape, effectively handing control of the province to the ANC.

Spent force

Currently the New National Party leader Marthinus van Schalkwyk is the Western Cape provincial premier.

The NNP's recent alliance with the ANC means that Van Schalkwyk will probably hold on to his position until general elections next year.

But the defections have hit the NNP hard, turning it from its position as a once-powerful national party into a much weakened regional force.

Schalkwyk's NNP party is weakened

In addition to the provincial defections, the NNP has also lost 9 out of its 28 MPs to the Democratic Alliance, the country's main opposition party.

DA leader Tony Leon welcomed the defectors saying they were the first swell of a tidal wave which would ultimately destroy the NNP and bolster the DA's position as the only national alternative to the ANC.

Voters disapprove

But the floor crossing frenzy has left a bitter taste in the mouths of voters.

An opinion poll conducted by Business Day newspaper, published on Tuesday, shows that South Africa's citizens are angry about the whole floor crossing episode.

They believe they have been betrayed and think the politicians are opportunists who pay scant attention to the wishes of the electorate.

Judith February of the Institute for Democracy in South Africa says the floor crossing exercise has not only left voters feeling disillusioned but also apathetic.

She says this might well result in a much lower turnout in next year's polls.

Political commentators predict that the next election might see the NNP, the descendant of the former all-powerful ruling National Party and the natural home for Afrikaners and mixed-race voters all but disappear as a force in South Africa's political landscape.