Varadkar has failed to meet Martin this year
The Taoiseach has consulted Mary Lou McDonald more often than Micheál Martin this year, with Mr Varadkar's diary showing he hadn't had a single meeting with the Fianna Fáil leader, whose party props up the Government.
Mr Varadkar's schedule, released under Freedom of Information laws, does not show any meetings between the two party leaders between January 1 and May 21 this year.
In that time, Sinn Féin president Ms McDonald has met the Taoiseach in private twice to discuss the ongoing stalemate in the Northern Ireland Assembly.
This week, Mr Martin issued a stern rebuke via reporters to Mr Varadkar about how the confidence-and-supply agreement is being handled. He called on the Fine Gael leader to show "basic courtesy" and request a meeting, rather than using the media to discuss the political deal, which props up his minority Government.
Mr Martin added: "No one has come to me on a one-to-one basis to say we want to have a look at the confidence and supply. Leo should talk to the leader of Fianna Fáil."
Speculation continues over the future of the agreement but a spokesman for the Taoiseach said issues related to it were being dealt with by staff on both sides.
In the same five-month period, Mr Varadkar has met twice with Ms McDonald.
The first meeting was held shortly after she was elected leader in February. Tanáiste Simon Coveney and Sinn Féin's vice-president Michelle O'Neill also attended.
The meeting was followed by a call with UK Prime Minister Theresa May.
A second meeting between the pair - this time without deputies - was held on May 1.
A spokesperson for the Taoiseach said the meetings were sought by Sinn Féin in connection with efforts to restore power sharing in Northern Ireland.
"The Taoiseach, along with the British prime minister, is a guarantor of the Good Friday Agreement. Similar meetings were held with parties from across the political spectrum at Stormont House earlier this year," the spokesman said.