Johann Lamont called for an end to "recriminations" at the giant Scottish refinery following the sacking of Unite union convenor Mark Lyon yesterday, three months after his suspended predecessor Stevie Deans resigned.
Unite has said it will take legal action on behalf of Mr Lyon, the union's UK vice-president, who was said to have been dismissed for not stopping Unite from commenting on fears of job losses at the plant.
Labour member Mr Lyon had been suffering from "a serious stress-related illness" as a result of his treatment by Ineos and was dismissed in his absence while visiting his doctor, according to Unite.
Mr Deans resigned in October following a long-running row over his involvement in the selection of a Labour candidate in Falkirk.
Ms Lamont said: "There can be no place for recriminations at Grangemouth.
"The workforce has accepted enormous changes to their pay and conditions to work with their employers at Ineos. They and their rights must be respected.
"The idea that they cannot choose their own trade union representatives is just plain wrong. And the idea that one trade unionist can be sacked because of what another trade unionist says is Dickensian.
"Ineos have received millions of pounds worth of public money from both the UK and Scottish governments. They cannot be allowed to ignore the most basic of their workers' rights."
Ms Lamont was handed overall control of the Labour Party in Scotland following a review in 2011, which widened her role from head of Holyrood's MSPs group to include all MPs and members north of the border.
Labour became embroiled in a dispute over claims that Unite tried to influence the selection of a candidate in Falkirk, prompting an inquiry at the behest of UK party leader Ed Miliband.
The row led Mr Miliband to announce reforms to the historic link between the party and unions - changes which were agreed yesterday by the party's national executive.
Linlithgow and East Falkirk Labour MP Michael Connarty tabled an early day motion at Westminster today calling for Mr Lyon to be reinstated and expressing "serious concern at the anti-trade union behaviour of Ineos".
The motion says: "This house is concerned that Ineos is in line to receive £9 million in grants from the Scottish Government and has applied for loan guarantee fund support from the UK Government for £150 million, and calls on the Government to make it clear to Ineos that actions in breach of international labour organisation conventions and UK laws is not acceptable in the UK."
Ineos has been contacted for comment.