Cable: Ministers will act if strikes harm the economy
Business Secretary Vince Cable was booed and heckled as he warned delegates at the GMB union's conference that co-ordinated strike action may lead to tougher union laws.
Unions say there could be significant public sector strikes on 30 June.
Mr Cable said that if the level of strikes remained low there would not be a compelling case for tighter laws.
The BBC's Political Correspondent Ross Hawkins reports.