Acting Prime Minister Pedro Sanchez unveiled his amnesty plan for Catalan separatists in a bid to keep himself in office.
But around 40,000 Spanish gathered in Spain’s capital Madrid to protest against possible plans, after an election he failed to win.
The protestors waved Spanish flags along with members from the opposition conservative People's Party travelled from across Spain to attend the rally in Madrid.
Reuters quoted protesters who expressed withdrawing criminal cases against the separatists would amount to granting an amnesty to "coup plotters".
“I am not in favour of the government that we have. To me this is a disaster because it is going to divide Spain totally," one of the protesters told Reuters.