Mr English's staff yesterday supplied the Northern Advocate with a copy of the rules confirming this.
Yet records obtained under the Official Information Act show that Government officials - and taxpayer resources - were working on the matter of Northland's bridges as late as two days before Transport Minister Simon Bridges' surprising announcement on March 9.
"What a Mickey Mouse operation," Mr Twyford said.
"Simon Bridges' office frantically trying to get transport officials to come up with a list of bridges, when Finance Minister Bill English says in Parliament that it is against the rules to use public servants to develop and cost a party's campaign proposal.
"It would be funny if it wasn't such a gross abuse of public money and the democratic process."
While New Zealand Transport Agency (NZTA) was asked to supply details about the number of highway bridges on Northland's state highways and estimates for replacing them, the agency was not informed about the Government's scheme. NZTA was told about it only the day before it was announced publicly.
Only three of the bridges were on NZTA's priority list for funding between now and 2018.
In answer to questions in the House by Labour MP Grant Robertson, Mr English said the costs of the scheme had not been referred to him because a political party's proposal (as opposed to a Governmental one) would not be costed by Treasury.