The conditional -(r)eba has two forms:
Following a consonant-stem verb, it takes the form of -eba:
行く ik-u → 行けば ik-eba
泳ぐ oyog-u → 泳げば oyog-eba
差す sas-u → 差せば sas-eba
放つ hanat-u → 放てば hanat-eba
死ぬ sin-u → 死ねば sin-eba
運ぶ hakob-u → 運べば hakob-eba
飲む nom-u → 飲めば nom-eba
走る hasir-u → 走れば hasir-eba
構う kamaw-u → 構えば kamaw-eba （note: /w/ disappears before vowels other than /a/,
so we end up with kama-u and kama-eba instead)
Following a vowel-stem verb, it takes the form of -reba:
食べる tabe-ru → 食べれば tabe-reba
生きる iki-ru → 生きれば iki-reba
So for short, we call it -(r)eba, using the parentheses to indicate both forms at the same time.
What about your example, 言われれば? Let's take this apart.
First, we'll start with consonant-stem verb 言う. Its stem is iw-, but the /w/ disappears before every vowel except /a/ in modern Japanese, which is why we end up with forms like 言わない iw-anai but 言う i-u. The /w/ disappears from iw-u and leaves us with i-u.
Next, we want to add the passive -(r)are- to this verb. We add it directly to the stem iw-, which gives us 言われる iw-are-. As you can see, we end up with a vowel-stem verb.
Last, we'll add the conditional -(r)eba. Since we're adding it to a vowel-stem verb, it takes the form of -reba, and we end up with iw-are-reba. As you can see, the two れs belong to different morphemes; you can't remove either of them.
For this reason, your alternative, *言われば, is ungrammatical.