Jordan's Islamists said on Wednesday they plan to boycott early polls expected this year over a "provocative" new electoral law, as analysts warned against an "official rigging" of the process.

A day after MPs endorsed the law, the Muslim Brotherhood said it was "in touch with centrist political parties and other groups to form a 'shadow government' and 'shadow parliament,' which means a definite boycott of the general elections."

"We expect many to boycott the polls. Those who bet on the participation of the Islamist movement in the vote are wrong and delusional," Zaki Bani Rsheid, deputy leader of the powerful Brotherhood, told AFP.

The new law increases the number of parliamentary seats to 140 from 120, including an expanded quota for women to 15 from 12.

It will go into effect after King Abdullah II approves it, giving voters the right to cast two ballots: one for individual candidates in their governorates and one for parties or coalitions nationwide.

But only 17 seats can be contested by party and coalition candidates.

"This is retarded and provocative... it will not produce representative lower house deputies. It does not honour those who have been demonstrating for reform since last year. It will kill political life," Bani Rsheid said.

According to the constitution, elections take place every four years, but Jordan held early polls in 2010 after the king dissolved parliament.

The Islamists boycotted those elections in protest at constituency boundaries, saying they over-represented loyalist rural areas at the expense of urban areas seen as Islamist strongholds.

"Under this law, the elections will turn into a crisis, instead of a solution," Bani Rsheid warned.

The king is pushing to hold crucial elections before the end of 2012 as Jordanians have held relatively small but persistent Arab Spring-inspired demonstrations almost every week since last year to demand sweeping reforms.

"(The) focus should be on the participation of all powers in the parliamentary political process," King Abdullah told the London-based Al-Hayat daily in an interview published Wednesday.

"The coming elections will be a test of intentions and plans," said the monarch.

He added that the Islamists' position on reforms "has become dictated by subjective considerations and regional inputs. This is the political reality in the region."

The Islamists have repeatedly demanded sweeping changes that would lead to a parliamentary system in which the premier would be elected rather than named by the king.

"There will be an official rigging of the election under this exclusionary law. There are different types of fraud. This is one of them," analyst Labib Kamhawi told AFP.

"Boycotting the elections would not be enough. The public should push hard to delegitimise the polls if they are held in line with this law, which has belittled people's reform demands."

Mohammad Masri, a researcher at the University of Jordan's Centre for Strategic Studies, expressed similar views.

"The law has failed to meet people's expectation under the current Arab Spring. All political powers will oppose it," said Masri.

"Thanks to this law, the upcoming parliament has already lost part of its legitimacy. Another large part will be lost of if people boycott the elections. Jordan is facing another political crisis."

Independent MP Khalil Atteih urged the Islamists not to boycott the polls.

"We understand that it is a controversial law that cannot satisfy all political powers, but I think boycotting the elections is not right and it will not change anything," he told AFP.

"The Islamists should take part and then work on improving the law. If such powers chose to boycott, elections would be meaningless."