The Government has given employers just six weeks to respond to the biggest change in employment relations in more than a decade.
The Department of Trade & Industry last week published a consultation document on two key aspects of trade union recognition procedures - but has given a deadline of 20 March to respond.
The release of the paper follows the launch of Personnel Today's campaign calling for better consultation to prevent new laws being rushed in without proper consideration.
David Yeandle, deputy director of employment policy at the Engineering Employers' Federation, said aspects of trade union recognition - such as access to staff - posed possible difficulties.
He said employers should have the chance to fully consider the consultation document.
"There are no European pressures and it is complex and potentially contentious.
"They would have been better advised to take that bit longer and give a full two months' consultation."
A CBI spokesman said he could not comment as the document had only just been received.
Jewson HR director Tom Flemming said the consultation period was unreasonable for "something complicated that is 30 pages long".
"Again we have been given six weeks to consult and one month to implement it. It smacks of being driven by a timetable rather than a need to get it right," he said.
A spokeswoman for the DTI said there had been wide ranging informal consultation over the planned law since 1997.
The Employment Relations Act allows for trade unions to be recognised or derecognised if sufficient staff are in favour.
The Act gained Royal Assent last summer and the Government plans to bring in the provisions relating to trade union recognition shortly after Easter.
Copies of the consultation are available on the Web.
By Helen Rowe
The consultation: six key points
• Preparations for trade union access to employees should begin as soon as possible
• The employer should not dismiss the union's proposals for access unless it considers them unreasonable. If it does reject them, it should offer alternative arrangements - pre