This new body, called RSPCA Campaigns, which is in the process of applying for charitable status, is the fifth charity to have registered with the Electoral Commission since the lobbying act became law in January.
The act says that, in the run-up to elections, charities, individuals or other groups spending more than £20,000 in England or £10,000 in other parts of the UK on particular "regulated activities", and if those activities might "reasonably be regarded as intended to influence voters", must register with the Electoral Commission as non-party campaigners.
Although charities must not engage in party political campaigns or support an individual candidate for election, charities have warned that the act will create a chilling effect, with some organisations cutting back on legitimate campaigns in order to be certain of not breaking the new rules.
A spokeswoman for the RSPCA said that because the RSPCA itself was a charity incorporated under a private act of parliament, it would not be able to register with the Electoral Commission.
The RSPCA has therefore created RSPCA Campaigns, which registered as a company limited by guarantee with Companies House on 5 September, and then with the Electoral Commission on 5 November, and has applied to the Charity Commission for charity status.
The spokeswoman said the new entity had been created "to deliver our public-facing campaigns, particularly during the regulated period, so as to avoid any unintentional breach of the new regulations".
She said: "We are registering on a precautionary basis. It is a case of 'better safe than sorry' given that this will be the first general election held under the new regulatory regime."
RSPCA Campaigns has three RSPCA staff listed by Companies House as its directors: David Bowles, head of public affairs at the RSPCA; Claire Robinson, its government relations manager; and Michael Ward, its director of resources.
The Electoral Commission's database shows a total of 31 registered non-party campaigners. Alongside RSPCA Campaigns and the other four charities, this includes seven trade unions, one individual person, several private consultancies and other campaigning groups including the online campaigns platform 38 Degrees and the Campaign for Nuclear Disarmament, which is the most recent registration.