In an expletive-laden email tendered at the Independent Commission Against Corruption on Monday, Mr Tinkler complained after the election that he had "dontated [sic] to the nats" and they were doing "f--- all" to approve a proposal by his company Buildev for a $1 billion coal terminal in Newcastle.

"We had a bunch of deadbeats before and now we have a bunch of pr--ks scared to make a decision," Mr Tinkler wrote in the April 20, 2011, email, in a reference to the former state Labor government and the newly-installed Coalition.

The ICAC is investigating allegations that Buildev was among a group of property developers that made illegal donations to a slush fund set up by an adviser to former state energy minister Chris Hartcher before the March 26 state election.

Property developers have been banned from donating to political parties since 2009.

The commission has previously heard that $66,000 was funnelled into the slush fund by Mr Tinkler's horse stud, Patinack Farm, as part of a "corrupt scheme" for Buildev to make secret donations to the Liberals.

Former police minister Mike Gallacher resigned on Friday after counsel assisting the inquiry, Geoffrey Watson, SC, accused him of being complicit in the scheme.

On Monday, it emerged that a further $20,000 was donated to the Nationals using four former employees at Mr Tinkler's Aston Resources.

“Mate need $20 [thousand] here to help these guys Nats will be running Ports,” Buildev co-owner Darren Williams wrote in a February 2011 email to Patinack Farm chief financial officer Troy Palmer.

Nationals MP Duncan Gay, who is not accused of any wrongdoing, was appointed ports minister after the 2011 election.

Mr Watson said there was evidence Mr Palmer drew the cheques that were used by the four former Aston Resources employees.

In a separate email in February 2011, Mr Williams asked Mr Palmer to "help" the Nationals with "3 lots of $5 [thousand] please mate" adding that the "boss is ok with this".

The state director of the Nationals, Ben Franklin, emailed Mr Williams in February 2011, saying the party would be "delighted to accept support for our state election campaign as long as it is not from prohibited donors". Mr Franklin is the Nationals' lead upper house candidate for the 2015 state election.

Earlier on Monday, Mr Williams agreed that Buildev had paid for flyers which damaged the standing of the then Labor Minister for the Hunter, Jodi McKay, who opposed the coal loader. He said the wording was provided by controversial Labor MP Joe Tripodi's "eyes and ears in Newcastle", Ann Wills.

Ms McKay gave extraordinary evidence last week that Mr Tinkler attempted to bribe her before the state election campaign and she referred his offer to the ICAC, the police and the NSW Election Funding Authority.

She said then Labor Treasurer Eric Roozendaal was aware of the bribe and she believed both he and Mr Tripodi, a former ports minister, attempted to undermine her because of her opposition to the coal loader.

Mr Williams texted a colleague before the state election that they needed to get anti-McKay material to the Independent candidate John Tate and the Liberal candidate Tim Owen, who narrowly won the seat from Ms McKay.

Asked by Commissioner Megan Latham whether local residents had been "hoodwinked" into thinking the flyers were from an independent source because they did not bear Buildev's name, Mr Williams said: "Um, yes."

On Friday Mr Watson had accused Mr Gallacher  of "hatching a corrupt scheme" with Mr Williams for Buildev to make donations to the Liberal Party using a slush fund called Eightbyfive.

The money was used to bankroll the party's successful 2011 election campaign for seats on the Central Coast and Newcastle. But Mr Williams denied on Monday that his close relationship with Mr Hartcher and Mr Gallacher was "borne out of payments made under the table to [Newcastle Liberal MP] Tim Owen's campaign".

Patinack Farm's Mr Palmer texted Mr Williams on April 19, 2013: "Have u got eightbyfive under control. We can't have patinack involved in an ICAC hearing."