The People's Assembly said it expected thousands of protesters will take to the streets on Saturday at locations throughout the UK including Sheffield to highlight those suffering "real hardships" due to the combination of rising fuel and food prices, inflation, and low pay.
Lifting the energy price cap on Friday will create an "impossible choice for many" - to eat or heat, said the campaign group.
A spokesperson for the People's Assembly said: "Public outrage over the cost of living crisis is growing fast, and our response is gaining momentum."
The Steel City protest will take place on Saturday from 11am to 12.30pm outside the Moor Market where there will be stalls and an open mic, as well as food provided for by Food Works.
In London there will be a protest outside Downing Street. Others will take place in cities including Doncaster, Birmingham, Cardiff, Hull, Liverpool, Manchester, Newcastle, Portsmouth and Southampton.
Former Labour leader Jeremy Corbyn, who will be speaking at the London demonstration, said: "With rising fuel, food and energy bills, the soaring cost of living is pushing millions into poverty, and the disgusting treatment of the sacked P&O workers needs urgent action from the Government.
"Demonstrations will be taking place all over the country, with thousands of people coming together to demand redistribution of wealth and power and decent wages for all, as well as justice for P&O workers."
Laura Pidcock, national secretary of the People's Assembly, said: "What people are experiencing is intolerable.
"No matter how patiently we explain that Government inaction over soaring energy and fuel costs and sharply rising food prices is deepening poverty, misery and hunger, it is met with at best indifference and at worst more of the same.
"We tell them about children going hungry and the Government shrug, politically speaking. Our anger and frustration with them must be directed and organised to build pressure on them."