A key part of the newly revised programme for government to end corporate donations to individual politicians and political parties could be open to constitutional challenge.

A senior lecturer in the Trinity College School of Law told the Sunday Tribune last week there was "definitely a freedom of expression issue" about such a move and that it was "not straightforward".

Dr Eoin O'Dell, an expert in freedom of expression, however, did point out that the Supreme Court here has previously upheld restrictions on political advertising for reasons that "could sustain the validity" of a ban on donations to individual politicians and parties.

But he noted that legislation attempting to regulate expenditure in US elections had been struck down by the US Supreme Court on freedom of expression grounds and that the European Court of Human Rights had also raised questions about such restrictions.

Emphasising again the broadcast ban on political advertising, O'Dell said it was an "open question" as to whether the arguments made in the US on freedoms of expression were "as strong in an Irish context". He added that the Irish constitutional protection of freedom of expression was "not a particularly strong one".

Speaking to the Sunday Tribune, environment minister and Green Party leader John Gormley said he was confident the ban would be legally sound. He accepted there had been "some talk" about potential issues surrounding such a measure and that the attorney general would have been contacted "on a lot of what was in the programme for government".

Gormley added that the way the government had approached the issue – allowing corporate donations to be made to a "political fund" which would then be distributed to political parties based on their electoral performance – should overcome any difficulties.

"Our understanding is that you do it in a way which enables people to contribute to the political process that's legally [okay]," he said, adding: "I believe that the way we've approached it is to ensure that we don't have undue influence on the political process".

He said that while the issue of freedom of expression had been raised, "it does infringe on other liberties when you have money influencing how decisions are made. If you have a situation as in the United States, where you have the best democracy money can buy, that is not conducive to a fairer, more equal society".