The Transport Workers Union may have been caught in a power-grabbing rort, after it was revealed that the union had bodged its numbers to get more sway in the Labor Party.

It is understood that the TWU’s formal influence in Labor has been slashed, along with its purported membership figures, after it was caught out by media inquiries.

Reports say the TWU had been telling Labor that it counted more than 38,000 members in NSW, making it one of the biggest and most powerful factions in the state.

But repeated probing by reporters forced the union to reveal its true numbers, the Sydney Morning Herald claims, and it is now listing just 17,800 TWU members in NSW.

The newly-adjusted numbers meant that at last weekend’s NSW state Labor conference, the TWU had just 23 delegates, down from 43, out of 429 union delegates in total.

In the ALP rulebook, state conference delegates elect members for the party’s committees, selecting a number of powerful roles.

There is the powerful party administrative committees, the public office selection committees (which chooses candidates for Parliament) and other internal governance groups.

Under the party rules, unions select half the delegates.

It has been alleged that now the TWU has shown its true hand, the conservative Shop Assistants Union will pick up some delegates.

A TWU spokesperson reportedly told Fairfax Media that it had “amended” its role in NSW Labor “in line with a clarification of party requirements”.

It said it would have just 23 delegates but declined to comment further on why it had inflated its membership numbers so dramatically.

NSW ALP’s right-leaning factions continue to be caught in webs of corruption and misconduct, as a royal commissions dig deeper into the dealings of the Health Services Union and TWU in particular.

The TWU is known as a power base for factional powerbrokers such as ALP vice-president Tony Sheldon, Senator Stephen Conroy, former senator and party official Mark Arbib and former NSW minister John Della Bosca, who is considered a key internal operative.

Meanwhile, public service agencies and departments have been sent a questionnaire to reveal whether they had made payments to the trade unions targeted by the royal commission into unions.

The bluntly-worded survey demands details of talks between the APS and unions, and calls for the disclosure of the job status of union officials since 2007.

The attorney-general's department is reportedly looking for details of dealings between the APS and the five unions in the Royal Commission: the AWU, the CFMEU, the HSU, the TWU and the CEPU.

“So far the commission has had limited attention on the Commonwealth, but this could change at any time should an allegation be made about the conduct of a minister, employee, agency or other matter in relation to trade union, trade union official, member or separate entity such as a slush fund,” the document states.

“In the event that a credible allegation were made against the Commonwealth, it is important that the Commonwealth is able to respond quickly.”

The ACTU's Tim Lyons told reporters that there may have been “political involvement or direction” in the production of the questionnaire.

“This document goes very much beyond anything in the Royal Commission's terms of reference and there's no evidence the Royal Commission has been at all interested in the Commonwealth public sector,” he said.

“It looks to me like this is an attempt to have sort of a shadow Royal Commission within the public service which would be deeply inappropriate.”