A TORY yobbo scandal erupted at the Commons last night, with Labour

accusing three researchers of breaking into Tony Blair's office. Speaker

Betty Boothroyd has ordered an inquiry, and the Prime Minister could be

confronted with this today.

The three Tory research workers were found in the Labour leader's

office last Friday and confronted by a member of his private staff who

alerted the Serjeant At Arms.

The incident follows a leaked memorandum from Tory Central Office,

urging Mr Major to set his back-bench ''yobbos'' on to Mr Blair.

The three research workers claim they wandered into Mr Blair's office

by mistake. They had been in the sports and social club which is

situated at the other end of Parliament, in the House of Lords, about

250 yards away.

The Labour leader's suite of offices is situated down a corridor

behind the Speaker's chair of the Commons, about 30 paces beyond the

Prime Minister's own offices. The Labour Party questions the three

researchers' explanation and is making a protest to the Commons

authorities.

The three, two men and a woman, were found in Mr Blair's private

office at 7.30pm by 47-year-old Ms Sue Jackson, head of his

administration.

One of them, Mr Andrew Hull, had a Commons security pass as a

researcher to the Tory MP for Bournemouth East, Mr David Atkinson, a

former chairman of the Young Conservatives in 1970-71.

Ms Jackson said last night: ''I was sitting at my desk on Friday

evening when I heard laughter and shouting. At first I thought it was

coming from downstairs. After several minutes I realised it was coming

from Mr Blair's office. I thought it was odd because everybody had gone

home.''

Mr Blair was in his Sedgefield constituency. It is alleged that the

three intruders were in his office for between five to seven minutes.

The Commons authorities are trying to discover what they did there in

that time.

Ms Jackson went on: ''I went through and saw three people coming out

of Tony Blair's office. I asked who they were and what they were doing.

They said they were lost. At no stage did they apologise or explain what

they were doing there.

''One of them rudely demanded to know the way out. I said I would have

to get security to show them the way.''

Ms Jackson then blocked the door and called security who took them

away.

Scotland Yard said only: ''No crime took place. The police are not

involved.'' Scotland Yard said the incident was a matter for the Commons

authorities.

The names of the other two are known to the Commons authorities but

have not yet been revealed.

One of the three was a citizen of the United States who was on

temporary work at the Commons. This had ended the previous Thursday

night.

Part of the security inquiry is to discover how it was possible the

three could blunder their way from one end of the Parliament building to

the other, from the basement to the principal floor, past the Prime

Minister's offices as far as the Opposition leader's suite at the end of

a corridor behind the Speaker's chair.

This incident, becoming known as ''Yobbogate'' after the Watergate

break-in at the Democratic Party's headquarters by President Nixon's

Republicans, will help to promote Labour's telling campaign on Tory

sleaze.

Mr Atkinson is a hard right PR man born in Essex in 1940.

He acted as Parliamentary Private Secretary to Mr Paul Channon for

eight years. He became chairman of the International Society for Human

Rights founded in West Germany by anti-Soviet emigres and has served as

president of Christian Solidarity International UK.

Mr Atkinson said last night that his researcher, Mr Hull, had written

to Mr Blair to apologise. ''We hope that he accepts that. I accept his

explanation as genuine.

''He and two colleagues found themselves in the office of the leader

of the Opposition having got lost in a part of the building where they

had not been before.

''Within seconds of them finding themselves in the office, which has

no sign on it and was not locked, a secretary came in and assumed the

worst. They explained that they were lost.''

Mr Hull has explained the situation to the Serjeant At Arms, said Mr

Atkinson, who understood that Mr Hull and his friends had been having a

drink in one of the bars.

The incident took place after both Houses of Parliament had risen for

the weekend and at a time when few MPs were still on the premises.