By Alastair Macdonald

BRUSSELS (Reuters) - The European Ombudsman called on Tuesday for the EU to tighten rules on commissioners taking appointments on leaving office after former chief executive Jose Manuel Barroso moved to a senior job at Goldman Sachs.

Heavy criticism has been aimed at the former Portuguese premier for taking the Brexit-linked London job at the U.S. bank, 20 months after stepping down as European Commission president.

Ombudsman Emily O'Reilly said adhering to technical rules did not absolve former staff of a wider duty to show "integrity".

"The EU treaty states that former commissioners should behave with integrity and discretion when it comes to certain appointments or benefits," the standards watchdog said, noting a "cooling off" period of 18 months when ex-commissioners must seek clearance for new jobs to avoid conflicts of interest.

"Any suggestion that the spirit of the law is being ignored risks undermining public trust in the EU," O'Reilly added.

Just two weeks ago, the Ombudsman condemned the failure of Barroso's commission to deal adequately with an unnamed former member who did not notify it of a job taken on. She called for revisions to its code of conduct and the creation of sanctions.

On Friday, Goldman Sachs said it had hired Barroso, a conservative who led the Commission for a decade until 2014, as an adviser and non-executive chairman of its international business.

He has said he hopes to bring his EU experience to bear as the bank's London operation deals with Britain's imminent negotiation of withdrawal from the European Union.

His appointment has drawn criticism, especially from the European left which has long viewed Barroso with distrust since his close involvement with U.S. President George W. Bush and British Prime Minister Tony Blair in launching the Iraq War.

French Finance Minister Michel Sapin joined the chorus on Tuesday, telling reporters in Brussels: "If you have loved Europe, you shouldn't do this to it, especially not now.

"But this doesn't surprise me from Mr. Barroso."

On Friday, Sapin's fellow Socialist, French Trade Minister Matthias Fekl, tweeted: "Doing citizens a disservice, self-service at Goldman Sachs: Barroso, shameful representative of an old Europe which our generation is going to change."

It was a view shared by the pro-Brexit deputy editor of London's Daily Telegraph, Allister Heath, who felt the appointment did no credit to the bank:

"If Goldman was trying to reinforce the view that it, and other big banks, are at the heart of a corporatist, unaccountable nexus that connects business, finance and politics – and whose elite members all end up working for each other and doing backroom deals with one another – then it hired the right person, in the right way and at the right time."

(Editing by Andrew Roche)