Unite has set up a strike fund, which has grown to £35 million, to finance industrial disputes.
The union is gearing up for a dispute involving North Sea workers based on Shell platforms.
Workers employed by the Wood Group are being balloted for strikes in a row over pay, with the result due on Wednesday.
Unite general secretary Len McCluskey told the union's policy conference in Brighton: "Our fighting-back culture is entrenched.
"For more than five years, we have never once repudiated our members taking industrial action.
"Although 95% of our time is dealing with and solving problems, on those occasions where our members need to fight, we have established a strike fund which is currently at £35 million to give them support and show employers that our members won't ever be starved back to work."
The conference will today debate the union's opposition to austerity.