CAIRO, Feb 23 (Reuters) - Egyptian liberal opposition politician Mohamed ElBaradei called on Saturday for a boycott of parliamentary elections which start in April, saying he refused to take part in "an act of deception".

Islamist President Mohamed Mursi called the elections on Thursday, aiming to conclude Egypt's turbulent transition to democracy which began with the overthrow of autocrat Hosni Mubarak by popular protests.

But ElBaradei, a former U.N. nuclear agency chief, noted that he had called in 2010 for a similar boycott of polls held under Mubarak, who was ousted the following year.

"Today I repeat my call, (I) will not be part of an act of deception," ElBaradei said on his Twitter account.

Islamists have used well-organised campaign operations to win every election since the revolution, while the liberal and leftist opposition has been beset by division.

The Muslim Brotherhood, which backs Mursi, dismissed suggestions that the elections, to be held in four stages from April to June, would lack credibility.

Essam Erian, senior member of the Brotherhood's Freedom and Justice Party, said the polls would be carried out under "complete judicial supervision" as well as being followed by Egyptian, regional and international media.

Voting would also be monitored by Egyptian and foreign civil society and human rights organisations, he said on his Facebook page, adding that he expected wide participation.

ElBaradei's call appeared to reflect confusion within the National Salvation Front (NSF), which groups a number of parties opposed to the Islamists - including his own.

Only on Friday NSF spokesman Khaled Dawood said the front would meet in the coming week to decide whether to participate. Previous opposition boycott threats have failed to materialise. (Reporting by Alexander Dziadosz; editing by David Stamp)