Those who use the word solidarity loosely to imply a politics based on the acceptance of mutual obligations where the rich contribute more to the common budget and the poor benefit from it can take comfort from modern democratic parties in the West.
In the UK as elsewhere all mainstream parties believe in three central tenets. They believe that the rich should pay more tax, and favour progressive tax systems. They believe that the poor should receive benefits from the state so no one need go without a roof over their head, food on their table and clothes on their back. They believe that all who can should work to provide for themselves and their families.
Although some on the left try to present the centre right and right as against any such system of social insurance, they are wrong. The debates are not about this central framework which all elected politicians of the main parties accept. The arguments are about the balance between the three tenets and how you best implement them.
What rates of taxation maximise an appropriate take from the rich ? Or do you wish to tax the rich so hard you drive them out of your country or they cease to be rich?
What level of benefits should you pass to the poor? All agree there has to be a ceiling but there are disagreements about how high it can be, both on grounds of affordability and on grounds of incentive to work.
The third issue raises the same questions. Should low income earners be exempt all tax? At what rate should in work benefit be removed? What are effective as incentives, and what is fair?
Small differences on these matters are often presented as fundamental disagreements, with centre right politicians presented as uncaring as if they wished to remove all support, and centre left politicians presented as wanting to bankrupt the country through inability to see there are limits to what the working population can afford by way of support to others. There is a general drift in democracies to more state spending and more state involvement, with more elected politicians campaigning for government to do things than campaigning for more freedom.