The government called off a meeting with student protest leaders yesterday on the eve of a scheduled dialogue to discuss election reform, saying it was unacceptable that protesters were using the occasion to incite more people to join the mass sit-in. Chief Secretary Carrie Lam Cheng Yuet-ngor said the talks would not be held because the government felt they would not lead to a constructive outcome. Lester Shum, vice-secretary-general of the Federation of Students, responded by calling on the tens of thousands of Hongkongers who had taken part in the Occupy movement to take to the streets tonight at 7.30 for an assembly in Harcourt Road, now renamed by protest leaders as "The Umbrella Square". About two hours before the chief secretary's announcement, pan-democratic lawmakers and protest leaders - including the Federation of Students, Occupy Central co-founders and the student activist group Scholarism - had vowed to escalate their disobedience and non-cooperation movement if the government failed to make "substantial responses" to their demands. These included the retraction of Beijing's restrictive framework for universal suffrage and the resignation of Chief Executive Leung Chun-ying. "With much regret, [after] the remarks made by student representatives in the past two days, especially this afternoon, I realise that the basis for a constructive dialogue has been seriously undermined," said Lam. She added that the government remained open to dialogue, but stressed that it would not accept protest leaders using the public interest as a bargaining chip by linking the dialogue results to their decision on retreating from protest sites. "Their unlawful actions must end as soon as possible," she said. However, she did not answer directly whether, or when, the police force would disperse protesters with force. Federation of Students secretary general Alex Chow Yong-kang said that Lam had used the students' remarks as "excuses" to call off the dialogue. "We were only saying that if the dialogue doesn't result in any progress, there will be such a movement, but officials said we had already started it. "If the chief secretary is sincere, the dialogue would still go on tomorrow." Joshua Wong Chi-fung, convenor of Scholarism, said they might mobilise another class boycott in secondary schools. Pan-democratic lawmakers suggested invoking the Legislative Council's Power and Privileges Ordinance to probe the police's handling of protests - such as the use of tear gas on demonstrators. But pro-government lawmaker Jeffrey Lam Kin-fung suggested launching a separate inquiry to counter the pan-democrats' move. And Tam Yiu-chung, chairman of the Democratic Alliance for the Betterment and Progress of Hong Kong, filed a petition to Legco president Jasper Tsang Yok-sing on Wednesday, calling for another probe into the organisation and financial sources of the protests. Meanwhile, a signature campaign has been launched to urge the government and student representatives to start talking as soon as possible. Signatories include former civil service secretary Joseph Wong Wing-ping and barrister Edward Chan King-sang. In a message to Hongkongers they said the current movement was not a revolution but a democracy movement initiated by students whose aim was not to overthrow the government.