Shadow health secretary Andy Burnham said he wanted reassurances that that a Government-backed inquiry into the conduct of industrial disputes was not a "political call".
"Of course if there's been intimidation it's unacceptable and that should apply to unions as well as employers," he told BBC One's Sunday Politics show.
"I think I need reassurance that this isn't a political call by Mr Cameron designed to report near the election, so you know we'll see how this develops."
More top news
Xavier Bertrand called for changes to the UK-France border agreement that would allow asylum seekers to apply in French 'hotspots'.
A bomb has exploded at the Brussels Institute of Criminology, after a car rammed through the barriers in the early hours of Monday morning.
It will be rather cloudy to start, with the odd shower for some.