The National Council for Voluntary Organisations is to publish a code of good practice for lobbying and campaigning by charities.
The umbrella body made the announcement in response to the publication of the government’s Transparency of Lobbying, Non-Party Campaigning and Trade Union Administration Bill on Wednesday.
Karl Wilding, director of public policy at the NCVO, described the bill as a "missed opportunity to restore some trust in politics".
He said the bill, which would introduce a statutory register for lobbying consultancies and tighter regulations for the amount organisations can spend on political campaigning during election periods, was not broad enough.
"People have a right to know who is trying to influence policy and why," he said. "The best way to achieve full transparency is with a universal register, run by an independent body, linked to a clear code of conduct.
"While charities aren’t generally thought to be part of the problem, we believe they should nevertheless have the highest standards of accountability and transparency.
"Given the narrow scope of this bill, we will create our own code of good practice for charities that lobby and campaign to make sure we retain the current high levels of public trust and confidence in charities."
An NCVO spokeswoman said the organisation had hoped the register would cover a wider range of lobbyists than just consultancies, and include others such as charities and trade unions. "If you’re going to do this we think it really should be universal," she said.
She said it was also disappointing that the bill did not include a code of good conduct for lobbyists, setting out standards of behaviour.
The NCVO will consult members about the scope of the code later this year.