The Prime Minister has just announced that public spending will be increased next year.

announced 是动词 announce 的过去分词形式，announce 的意思是"宣布、通告"，由前缀 an-（表示"向"）和词根 nounce（来自拉丁语 nuntiare，意为"告知"）组成。在这里表示"正式公开地告知"。 过去分词形式 has announced 构成现在完成时，强调动作已经完成并对现在产生影响。