Any attempt to conduct a de facto referendum on Hong Kong's electoral reform would be inconsistent with the Basic Law, Secretary for Constitutional and Mainland Affairs Stephen Lam Sui-lung said yesterday, three days after Beijing sent the same message to pan-democrats. Five lawmakers from the Civic Party and League of Social Democrats plan to resign, triggering by-elections they will contest on a platform of genuine universal suffrage and the scrapping of Legco's functional constituencies. They say the exercise will be a de facto referendum. On Friday the State Council's Hong Kong and Macau Affairs Office said any 'so-called referendum' would be inconsistent with Hong Kong's legal status and a 'blatant challenge' to the Basic Law and the central government's authority. Lam said electoral changes could only be carried out using procedures prescribed by the Basic Law. 'Any arrangements to promote a referendum outside these constitutional procedures would not be consistent with the Basic Law,' the minister said. 'Also, whatever the outcome of this movement for five legislators to resign from geographical districts, it will not change our constitutional procedures for adopting new electoral arrangements.' Lam was asked whether the proposal by the two pan-democratic groups was unconstitutional, but he sidestepped the question. He also said the Hong Kong government would not propose a law to allow referendums. Under the two parties' plan, five pan-democratic legislators - one from each of the geographical constituencies - will announce next week that they are resigning. They say the subsequent by-elections will allow residents to express their position on constitutional reform through the ballot box. However, there are still uncertainties about the arrangements for by-elections. Some Beijing-friendly lawmakers say they may block the government's application for financing to conduct them. The Constitutional and Mainland Affairs Bureau has estimated that the by-elections will cost HK$150 million. Wong Kwok-kin, vice-president of the Federation of Trade Unions, said: 'People may mistake the by-elections for a referendum. Endorsing such expenditure may just add heat to the debate.' Two pro-government political parties, the Democratic Alliance for the Betterment and Progress of Hong Kong and the Liberal Party, said they had not yet decided whether to support the financing proposal. Liberal Party chairwoman Miriam Lau Kin-yee said: 'It is a waste of taxpayers' money.' Hong Kong delegates to the National People's Congress and the Chinese People's Political Consultative Conference are expected to discuss constitutional reform today at their annual meeting, which is being held in Zhuhai. It will be hosted by Qiao Xiaoyang, deputy secretary of the National People's Congress Standing Committee.