Mrs Whitlam said around 100 MPs have replied offering their support and she is pleased with the campaign’s progress.
Her son Harry, 11, from East Ardsley, died after he was struck by a reversing tractor at Swithens Farm in Rothwell in 2013.
However, the driver of the tractor, Gary Green, who was over the drink drive limit, could not be prosecuted under road traffic laws because the incident took place on private land.
Mrs Whitlam is campaigning for that loophole to be closed with the introduction of what has become known as “Whitlam’s Law”.
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She said: “we are pleased with how things are progressing. It’s a slow process but we are gaining support from other MPs who are backing the changes we are trying to make.”
Alec Shelbrooke MP (Cons/Elmet and Rothwell) held an adjournment debate on the issue in the House of Commons last July.
Last week in the House of Commons Mr Shelbrooke said he was no clearer as to the Government’s position.
Andrea Leadsom MP, leader of the House of Commons, told Mr Shelbrooke: “I have been reassured that discussions are taking place between the Road Safety minister and the Minister for Disabled People, Health and Work to look at what more can be done.”
Last October Mrs Whitlam met MP Jesse Norman, Under Secretary of State for Roads, Local Transport and Devolution.
She spoke to the Minister in London alongside her constituency Mr Shelbrooke and Amy Clowrey from Switalskis Solicitors, which has supported the family in their campaign.
Mr Norman said it was now time to “rethink the relationship between drink-drive laws and public and private land.”
Green, from Robin Hood, near Rothwell, was sentenced at Leeds Crown Court in 2016 to 16 months in prison for health and safety violations.