UPDATE 1-'Insane', UK's Johnson criticises EU over N.Ireland post-Brexit trade

(Adds Irish foreign minister, background)

LONDON, Jan 26 (Reuters) - British Prime Minister Boris Johnson accused the European Union on Wednesday of implementing part of the Brexit agreement covering trade with Northern Ireland in an "insane and pettifogging way", comments Ireland dismissed as unhelpful.

"The EU is implementing this in an insane and pettifogging way and we need to sort it out," Johnson told parliament, complaining that the so-called Northern Ireland protocol was stopping some food delivers and other difficulties.

Irish Foreign Minister Simon Coveney said the comments were unhelpful as the European Union was bidding to build trust with new lead British negotiator, Foreign Secretary Liz Truss, who took over last month from David Frost.

Coveney, a key figure in the negotiation of the protocol, told the upper house of the Irish parliament that he welcomed the "constructive atmosphere" of recent talks involving Truss and that he hoped progress could be made in the coming weeks.

Truss at the weekend said she believed there was a "deal to be done" on the impasse, which centres on trading arrangements for Northern Ireland. (Reporting by William James and Conor Humphries, writing by Elizabeth Piper; Editing by Alistair Smout and Kylie MacLellan)