The call, on Monday, came as the European Parliament's internal market and consumer protection committee was due to discuss the Commission's proposal for an accessibility act.
Stevens and Šoltes joined demonstrators outside Parliament in a show of strength ahead of the meeting.
Šoltes, a Slovenian Greens deputy, said that millions of people in Europe are still excluded from using basic products and services that are taken for granted by others.
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These, he told the 200-strong gathering, included withdrawing money from a cash machine, entering a bank or any public building and using the metro.
"All are impossible for many people, including persons with disabilities and older people," he said.
The act is a proposal for a law that could make several products and services in the EU accessible for all citizens, including 80 million persons with disabilities and 190 million people aged 50 and older.
The draft legislation provides the opportunity to harmonise the accessibility obligations and requirements for products and services within the EU's internal market, reducing barriers and reducing costs for persons with disabilities, older people and all citizens.
Stevens, a Belgian ECR group member, told this website that she was taking part in the demonstration partly because of deep concern about the committee's recently published draft report.
"The committee's report is watering down the proposal for the act to such an extent that fundamentally important parts of it may be lost.
"The aim of today's demonstration is to call on the committee and parliament to adopt a stronger and more ambitious position on the accessibility act."
She added, "It is vital that all MEPs realise the full importance of this act. Without it, many rights, including the freedom of movement, will continue to be denied to people with disabilities."
The two MEPs, along with rights groups, are calling on Parliament to broaden the scope of the proposal by including the built environment and key products and services, such as household appliances and hotels.
The act, they say, should also have a strong relation with other EU legislation and not exclude micro, small and medium-sized enterprises (SMEs) from applying the requirements of document.
The demands are echoed by the President of the European Disability Forum, Yannis Vardakastanis,who said, "Accessibility is a prerequisite to live independently and be included in society.
"We are calling on the European Parliament to keep its role as the front runner for the rights of its citizens and support a strong and ambitious accessibility act that will bring a real change in the lives of all people in Europe."
Further comment came from the Vice-President of Social Platform, Maciej Kucharczyk, who said, "Accessibility is of paramount importance to ensure that our societies are inclusive and leave no one behind.
"European civil society is gathering today to raise the voices of millions of people facing barriers in access to goods and services and who would remain excluded from mainstream society if the European Parliament votes to water down this vital and timely act."