PRESSURE is mounting for a review of the law which imposes restrictions on ex-prison inmates who want to run for elections. The United Democrats' spokesman on security affairs, James To Kun-sun, said the party would move to amend the law if the Government took no action. He was joined by pro-democracy activist Lau Shan-ching - jailed in China for 10 years for ''counter-revolutionary activities'' - who called the law completely unreasonable. But a government spokesman said it was essential that ''candidature requirements are sufficiently stringent''. Under the Electoral Provisions Ordinance, people who have been convicted of an offence which carries a jail term of more than three months are disqualified regardless of where the conviction took place. An eligible candidate must also have resided in Hong Kong continuously for the 10 years preceding the election. Mr To said it was not appropriate to link the territory's electoral system with the legal system in other countries. ''We cannot simply look at overseas legislation and the length of their sentences, equate that with the case of Hong Kong and reject certain people from running,'' he said. Mr Lau, who served his 10-year term in Guangdong, said the law should be amended quickly. The 41-year-old activist wants to run for this year's Kwai Tsing District Board election, but is not sure whether he qualifies. Mr Lau said he should not be turned away because of the punishment he suffered in China. ''I was jailed for counter-revolutionary activities, which is not on the statute book of Hong Kong.'' he said. ''After all, it was a political persecution.''