MRS Thatcher yesterday launched an attack on the worldwide threat

posed by the greenhouse effect, with nuclear power spearheading the

assault.

A Downing Street seminar summoned by the Prime Minister also opted for

greater energy conservation measures and better use of substitute fuels.

The Government will press ahead with a nuclear programme to combat the

worst effects of global warming caused mainly by carbon dioxide

emissions from coal-burning power stations.

However, Ministers realise public fears about nuclear safety need to

be reversed if the campaign is to succeed.

They will highlight the major threat from global warming and ozone

depletion and contrast it with the ''negligible'' risks of nuclear

power.

Mr David Cope, director of the United Kingdom Centre for Economic and

Environmental Development, said after the seminar that nobody should be

under any illusion about the Prime Minister's commitment to tackle the

greenhouse effect.

''Before I came here I was a sceptic but I am now definitely convinced

that she is deeply concerned about the long-term environmental impact

and I think she intends to try and articulate and take the lead in an

international way to do something about this,'' he said.

Mrs Thatcher and other senior Ministers were briefed by leading

scientists during the ''teach-in.''

Afterwards it was being stressed that the amount of carbon dioxide in

the atmosphere is increasing at the rate of 0.5% per annum, a factor

which means the planet will undergo a temperature increase of between

1.5 to 4.5 degrees centigrade from the middle to the end of the next

century.

Sea levels are consequently expected to rise between 20 centimetres

and 1.5 metres, swamping low-lying islands like the Maldives in the

Indian Ocean. Damage to the ozone layer could mean more cancer-causing

ultra-violet rays reaching the Earth's surface.

Professor James Lovelock, author and expert on the greenhouse problem,

warned that the effect of an increase in the amount of carbon dioxide in

the atmosphere would be a series of climatic surprises. The 1987

hurricane which hit Britain was an example and the hole in the ozone

layer was another surprise discovery.

''None of us really know for sure when the problem will get out of

hand. But it is very unlikely we shall reach the next decade without

there being fairly major problems occuring perhaps in sea level terms,''

he said.

Ministers see a combination of nuclear, energy saving and substitute

fuels, including renewables, as the only way to make the biggest

''dent'' in the build-up of greenhouse gases in the atmosphere.

The Government hopes to introduce a Green Bill with measures to

safeguard the environment at the first available opportunity.

The Bill is expected to include a #2 billion programme for cleaning up

sulphur dioxide emissions from power stations, the main cause of acid

rain, but other firm decisions have yet to be taken.

* Democrats leader Mr Paddy Ashdown yesterday called for a complete

halt to nuclear power in Britain by the end of the next three decades.

In a speech timed to coincide with the third anniversary of the

Chernobyl nuclear power station disaster, he accused the Prime Minister

of ''nuclear-mania.''