They will deliver the petition, signed by more than 113,000 people, to 10 Downing Street ahead of an official inquiry into the All-Party Parliamentary Group (APPG) on body image.
Both models will present evidence from their own experiences, and the inquiry will also hear from fashion industry experts, including model agency managers, a columnist and fashion lecturer, PA reports.
The petition was launched by Nelson, 23, after she was told by her modelling agency to keep losing weight until she was "down to the bone".
In a letter to Caroline Dinenage, Minister for Women and Equalities, she wrote: "When I walked into one of the UK's biggest model agencies last year they told me I ticked all the boxes except one - I needed to lose weight. So I did.
"Four months later I lost nearly a stone, two inches off my hips. When I returned to the same agency they told me to lose more weight, they wanted me 'down to the bone'."
She highlighted that events such as London Fashion Week draw more attention to the need to protect young girls and boys who are being pressurised by the fashion industry to become "dangerously thin," and enshrine the need for protection in law.
Her letter added: "Modelling can be a very lonely place, especially for girls working internationally who are away from the usual support network of friends and family.
"When models travel overseas they are often put into shared accommodation with other models, and being surrounded by girls who are all striving to stay thin can perpetuate bad eating habits and encourage eating disorders.
"I've been on shoots for up to 10 hours where no food is provided - the underlying message is always that you shouldn't eat."
Earlier this year, MPs in France voted to make it a criminal offence to hire very thin models in a bit to curb anorexia. Those who do now face hefty fines and even a six-month prison sentence.
MP Caroline Nokes, chair of the APPG, is campaigning for similar rules in the UK and will join Ms Nelson in taking the petition to Downing Street.
The petition can be viewed and signed here.