Why did Margaret Thacher resign as prime minister?

Margaret Thatcher resigned as Prime Minister in November 1990 primarily due to declining support within her own party and increasing public discontent over her policies, particularly the unpopular Community Charge (poll tax). She faced a leadership challenge from within the Conservative Party, and after failing to secure enough backing in the first round of voting, she chose to step down to avoid a potentially damaging defeat. Her resignation marked the end of her 11-year tenure, during which she had implemented significant economic and social reforms.