A DEFIANT Tony Blair declared last night, amid growing dissention

about changing Labour's constitution on nationalisation: ''I am doing

this not because it is easy but because it is the right thing to do.''

At stake is the 70-year-old commitment to public control of industry

and the markets.

The Labour leader used a keynote speech to captains of European

industry in Brussels to demand party support for his reform of the

notorious Clause Four, which defined socialism for the fledgling Labour

Party in 1918.

Mr Blair wants to persuade the nation that Labour no longer believes

in nationalisation as an economic solution.

He turned on his critics in the Labour Party, who are seeking to

thwart him at a special conference on ditching Clause 4, on April 30. At

the Commons last night, 50,000 letters were despatched to constituency

parties and others urging resistance.

''The Labour Party is not a preservation society,'' he said. ''Those

who seriously believe that we cannot improve on the words written for

the world of 1918 when we are now in 1995 are not learning from history

but merely living in it.''

Mr Blair, anxious to reassure British industry, stated there would be

''no ambiguity about our convictions and our determination to carry

through our radical programme in government''. He promised: ''The new

constitution will state what we actually believe.

''We believe that there are key services that should remain in public

ownership. Equally, it is not and has not been for decades, the policy

of this party to argue for the wholesale nationalisation of industry. We

need, as well as strong public services, a dynamic modern market

economy. The one assists the development of the other.''

Mr Blair was irritated by the action of some of his Euro-MPs taking an

advertisement in The Guardian yesterday opposing his Clause 4 reforms,

on the eve of his carefully prepared speech in Brussels defining

Labour's attitude to Europe, including the support of monetary union.

Three of the 32 Labour MEPs yesterday dissociated themselves from the

action of MP Alex Falconer (Mid Scotland and Fife), who the Tories

claimed yesterday was using Shadow Chancellor Gordon Brown's

constituency office, which he shares, in Inverkeithing to promote

dissent.

However, left-winger Diane Abbott, a member of the Labour's ruling

National Executive said: ''The party did not pick this fight with Tony

Blair, he picked this fight with the party. He can win at this

conference but what is clear is that he will not win the support of the

majority of constituency parties.''

Tory and Liberal Democrat opponents were rejoicing at Mr Blair's

discomforture. Mr Jeremy Hanley, Tory chairman, issued a factfile called

Reforming Clause 4 -- the politics of presentation -- to try to show

that Mr Blair is not changing anything.

Liberal democrat Treasury spokesman Malcolm Bruce hit harder. ''Even

if Blair wins the Clause 4 vote, people will know that, in power, the

Labour leadership would need to rely for its survival on the 50% of its

members whose beliefs are totally at odds with those of Mr Blair.''

As Mr Blair arrived in Brussels last night, he received a resounding

endorsement of his stand on Clause 4 from the former Labour leader Mr

Neil Kinnock.

Mr Kinnock accused Clause 4 supporters of living in the past. Clause 4

was merely symbolic, he claimed.

He said: ''I don't think a democratic socialist party should get its

defining principles from an icon.''