A building company has secured a temporary High Court injunction against the Building and Allied Trades Union (BATU) after claiming the union is the "prime mover" in an ongoing "campaign of intimidation" of its workers on construction sites in Dublin.

Collen Construction last week secured a court order committing to prison three unemployed bricklayers after the men refused to give undertakings to stop picketing a Collen site at Ballybrack, Dublin in a row over securing jobs for local people.

During pickets this week of its site at the Hugh Lane Municipal Gallery, Frederick Lane, Dublin, by picketers who said they were supporting the jailed men, Collen said that some of its employees were kicked and hit by picketers blocking access to the sites and that one picketer had "pulled a knife" on another employee.

Collen claims the actions of BATU are having "a catastrophic effect" on its business in circumstances where there is no trade dispute between Collen and BATU and where both parties are bound by a registered employment agreement relating to the engagement of workers on construction sites.

Leo Crehan, a director of Collen, said he was told by one picketer at the Hugh Lane site on Wednesday last, who identified himself as Tom O'Connell, that BATU was 400 years old and the method of picketing a site to secure employment was "a tried and trusted one" which worked on all occasions. Mr O'Connell and another picketer had said their colleagues "would fill Mouintjoy if necessary in order to achieve their demands".

Mairead McKenna, for Collen, yesterday secured an interim injunction, returnable to Monday next, from Ms Justice Mary Laffoy against the union and Mr O'Connell, whose address was given as care of BATU.

The order restrains pickets of sites at UCD, Belfield, and the Hugh Lane site and also restrains the defendants from breaching grievance and resolution procedures in a registered agreement with the Labour Court.

The firm employs about 110 on the two sites on building projects valued at €27 million. It also employs sub-contractors.

In an affidavit, Mr Crehan said there had been pickets of its site at the Hugh Lane gallery on Wednesday afternoon by some 200-300 people who had marched from a rally at the Central Bank and were addressed by Richard Boyd Barrett of the People Before Profit Alliance.

Mr Crehan said the crowd were extremely loud and intimidating. He heard shouts of "Free the Ballybrack Three" - a reference to the jailed bricklayers - "jail the contractors", "come out you culchies" and "come out you scabs". Pieces of timber were alsdo thrown onto the site.

Pickets were also placed on Thursday at Collen's site on the UCD Belfied campus. The picketers unsuccessfully sought to block employees entering onto the site.

Pickets also arrived at Collen's site at the Hugh Lane gallery on Thursday morning and locked the gate with a chain and padlock.

Mr Crehan said Socialist TD Joe Higgins was standing beside a group of picketers sitting on the steps of the gallery. When he asked Mr Higgins why he was supporting an illegal picket, Mr Higgins had said it was not illegal and he was there to show his support for the jailed men.